Google's Ice Cream Sandwich, Android 4.0, is the biggest update the popular smartphone platform has received in more than a year. It adds dozens of features, changes and improves the interface, and makes much better use of the latest smartphone hardware. It may finally make Android tablets viable, too. At launch, though, it's missing a few things, most notably Flash and Facebook support, which mean that you may do well waiting a few months before scooping out some Ice Cream for yourself.

The New UI

The new Ice Cream Sandwich UI integrates elements from the phone and tablet UIs into, hopefully, a harmonious system which will work equally well on phones and tablets.

The look employs a lot of subtle shading, a lot of compositing, and a lot of depth, especially compared to the very flat screens in Gingerbread. Powerful GPUs seem to be assumed here, as screens and images almost always have multiple layers. But a generally spare design keeps it feeling like Android: functional, not showy.

The new lock screen shows the date, time, and your wallpaper. To unlock the phone, swipe right, or swipe left to jump directly to the camera. That takes you to one of five home screens, where you can place widgets or icons at will. You can now create folders on your home screens, and the folder layout is witty and smart: it shows the icons of various items in the folder, stacked. Four favorite icons, now customizable, stay at the bottom of every home screen.

The app drawer is still there, but now it's two-paned: you can flip between apps and a full-screen display of available widgets. Sliding between pages of apps, it looks like each one reveals the next under it. The multitasking interface borrows from Honeycomb: press a dedicated "multitasking" soft key, and thumbnails of the last several apps you've used ghost above the display. (There's that multi-layer compositing again.)

There are a few frustrating touches. Android's old physical buttons have been replaced by virtual buttons, and they can be a little elusive. On some screens, such as the camera, all the virtual buttons go away, leaving only gray dots. The new Menu button also moves around from app to app, and sometimes you have to search for it. As a longtime Android user, I want to know where my Home and Back buttons are at all times.

Text selection is also still an issue. To select text to copy or paste, you're supposed to long-press and then move two nicely-sized bookends, but in some apps I found the selection bookends appeared when I was just trying to drag or scroll the screen.

The Cool Features

Along with the new UI come a bunch of great, entirely necessary new features. Improved Web browser performance is a big deal. The browser benchmarked at double the speed of the Android 2.3 browser, and it has very useful new pop-down menu options: you can easily switch between mobile and desktop views and store pages for offline reading. The browser now scores 100 on the Acid3 test of HTML5 compatibility, as opposed to 95/100 for the Gingerbread browser; font rendering, especially, has been dramatically improved.

Android's contact book got a refit as well. It's borrowed a bit of its look from Windows Phone 7, integrating Twitter, LinkedIn and some other minor social networks, with multiple-pane contact cards showing your friends' most recent status updates, plus the amusing ability to auto-block calls from any of your contacts. While you can manually join contacts from multiple sources, I would have liked to see a smarter auto-join algorithm like the one HTC uses in its HTC Sense software.

The Gmail app is much better looking. You can create new messages without having to press the menu button, there's a bit more preview text for each message in the message list, and in general the new appearance, with more grays and the new Roboto font, is more appealing.

The Camera app has been dramatically improved. It's much, much faster, to the point where I was wondering whether I'd actually taken a picture because it was so fast. That's something we've seen on some devices like the HTC Amaze but appears to be standard in ICS. The new music player integrates with Google Music, so it has a built-in store and lets you stream from your cloud music library. It also shows a cool little VU meter when you're playing songs, and has an extensive graphic equalizer.

I really like the new data-management screen in Settings, which lets you monitor how much cellular data you've been using day by day, project your usage for the month, and issue automatic warnings. In this era of data caps and prepaid phones, this is an extremely useful utility.

Potential in APIs

ICS brings a lot of underutilized Honeycomb features to phones. They were underutilized because nobody was buying Honeycomb tablets and thus the features never had a market. But they're exciting: accelerated 2D and 3D graphics APIs (read: better games), more Bluetooth profiles and support for more input devices (read: better game controls), and enterprise-level encryption for business devices. Phone makers have been adding some of those features to Gingerbread, but now hopefully they'll have a wide enough base to actually take off.

In ICS, a new "social API" lets third-party social networks integrate into the address book. Third-party apps also get better access to the calendar, and there are a bunch of new streaming media and codec features. Let's not forget the browser, either: a more HTML5-friendly browser means better Web apps. I'm also intrigued by Wi-Fi Direct, which lets devices connect directly to each other without a router or hotspot. That could eliminate the need for syncing cables, if it's easy enough to use.

The Dumb Features

Fourteen pages of upgrades leaves a lot to like, some stuff to ignore, and some stuff that's just silly. Take "face unlock." This gimmick unlocks the phone when it's presented with your face, or a picture of your face, or something that looks kind of like your face. Whoo-hoo. "Live effects" is a silly GPU demo that lets you squish faces or put new backgrounds behind videos you're recording. Sigh.

I'm also cool on gimmicky NFC tricks like Android Beam, which lets two ICS phones share apps and data by bumping them together. The short-distance networking technology NFC has been slow to take off in the U.S. in general. Similar features to Beam have been tried many times (all the way back to the old PalmPilot days), but have never been big sellers.

Every OS has dumb features, and these aren't a minus because they don't seem to have taken attention away from more useful pursuits. But they're getting more press than they deserve, and they shouldn't be part of your buying process.

The Missing Features

Three major missing features may be showstoppers for some smartphone buyers. Fortunately, we're pretty sure that smartphone makers such as HTC will fill these gaps, but until then, these are things Android 2.3 does better.

The first is Flash. ICS phones show less of the Web than earlier models of Android do, because the Adobe Flash plug-in doesn't work. Adobe said it'll have a version working by the end of the year, so that problem should be solved soon. Adobe's move to stop mobile Flash development, in my mind, doesn't change anything, as far too many sites still require Flash. Maybe Flash won't be a useful mobile feature in two years, but it's useful now.

The second, more important issue, is Facebook. Because Google and Facebook are having a nasty spat over APIs, you can't absorb Facebook contacts into your address book and can't integrate Facebook into the messaging apps. This is unlikely to be fixed on the Nexus phones, but I expect HTC and Samsung to fix it on other devices.

Third, some (but not all) ICS devices will lack Mass Storage support. This means those phones won't show up as a drive when you plug them into a Mac; you need to use a clumsy, separate file-transfer app. ICS phones still show up as drives on PCs, because Windows supports the MTP protocol the OS is now using. This could be a deal-breaker for Mac owners.

Finally, ICS causes some problems with the Android Market. Not all apps are compatible with ICS (the Kayak travel-booking app, for instance, had trouble executing searches on my phone) and if the app developers lazily didn't include a "Max API" tag when they submitted their app, the non-functioning apps will show up on ICS devices. This is a bad user experience. Maybe it isn't directly Google's fault, but users will still suffer.

Competing smartphone OSes aren't necessarily much better. lacks Flash, Facebook integration, and Mass Storage as well. has Facebook integration, but not Flash or Mass Storage. RIM's lacks Flash but has the other two features. Still, though, as these features were popular on Android 2.3 phones, it's tough to see the platform backsliding.

Comparisons and Conclusions

There are four major players in the smartphone OS world right now. In order of market share, they are Android, Apple's iOS, RIM's BlackBerry 7, and Microsoft's Windows Phone 7.

Android hit its lead position by offering the most flexibility for the most people. By being fully open-source and joining the tablet and phone branches of the OS, Ice Cream Sandwich continues that trend. We're going to see a flood of ICS phones and tablets over the next year, on every carrier, in different shapes and sizes. And ICS is ready for new high-res displays and quad-core chips.

ICS isn't the best OS for everyone, but it's the best OS for the largest number of people. iOS is easier to use and has a better app marketplace in every way; the Apple App Store is larger and better curated. But Apple's single phone form factor counts out everyone who doesn't want a slab-style, all-touchscreen phone with a 3.5-inch screen and no 4G.

BlackBerry 7 has excellent messaging apps and is very manageable, but RIM is switching to BBX soon; BlackBerry 7 is the last iteration of an ancient and doomed platform. Windows Phone 7 is extremely easy to use and better for Facebook lovers and beginning smartphone owners than ICS is. But its third-party app selection is far inferior to either Android or iOS, and it has relatively few phones on CDMA carriers.

Who's Ice Cream Sandwich coming to? Of phones released by U.S. carriers, HTC has announced future upgrades for the Vivid, Rezound, Sensation, EVO Design 4G, EVO 3D, and Amaze 4G. Samsung said it's coming to the Galaxy S II. Sony Ericsson said it's coming to the Xperia Play, and Motorola confirmed it'll be available for the Droid RAZR.

So you should scream for Ice Cream. If you're buying an Android phone right now, make sure that the manufacturer plans an upgrade. If you're considering buying a smartphone soon, keep an eye out for ICS phones which fill the OS's gaps, such as HTC and Samsung phones with better Facebook integration.