Google's Android 4, codenamed Ice Cream Sandwich (ICS), debuts later this month on the much-anticipated Galaxy Nexus smartphone. This major new version of Android includes a redesigned user interface that promises a uniform experience across tablet and smartphone form factors, and it delivers new features and a wide range of improvements across the core application stack.

We already gave you a look at the Galaxy Nexus earlier this month in a hands-on review of the hardware. Now it's time to take a close look at the operating system and the ICS user experience.

User interface

The look and feel of the new interface is largely inherited from Honeycomb, the previous tablet variant of Android. ICS carries over Honeycomb's Tron-inspired "holographic" visual style, but the design has been refined to work well on multiple screen sizes.

The Android 4 design is functional rather than expressive. It uses a simple color palette and doesn't have much texturing or depth. Most of the user interface elements are flat, depicted with straight lines and solid colors. Drop shadows are rare, used only to embellish the effect of layering in top-level user interface elements such as toolbars.

The muted style of the applications, which mirrors the restraint of Google's new look on the Web, contrasts oddly with the style of the home screen and notification panel. I like the design of the application user interface controls, but I'm less impressed with the new home screen. Pairing heavy transparency with a busy animated background on a phone-sized display creates plenty of visual clutter. Fortunately, configuring the phone to use a dark solid color for the home screen wallpaper largely fixed that problem.

Android 4's new look won't appeal to everyone, but it's definitely an improvement over Gingerbread—and it conveys a sense of identity and visual coherence that were previously lacking.

New typeface

One of the major changes in Android 4 is the introduction of a new typeface called Roboto that was created specifically for the platform. Some technical characteristics of Roboto have attracted criticism from typography enthusiasts, but it does look much better on the high-density display of the Galaxy Nexus than it does on a conventional computer monitor.

After using Roboto extensively on the Galaxy Nexus, my only complaint is that the individual characters seem a bit too narrow. It feels tight at small sizes, but it's comfortable to read at larger sizes and works well as a content font in the stock Web browser.

Home screen

The new home screen in ICS is more powerful than was its Gingerbread predecessor. Like previous versions, it allows users to place widgets and icons across several different pages, which can be changed by dragging to the left or right. Five pages are available, each of which can accommodate up to 16 icons in a four-by-four grid. Like Honeycomb, the home screen in ICS displays a helpful grid when you drag items.

At the bottom of the home screen sits a fixed dock that's visible across all of the home screens. The dock can hold four icons in addition to the standard button for invoking the launcher, and the new home screen finally allows users to customize the contents of the dock (a feature that wasn't previously available). Folders can even grace the dock now.

Folders in ICS are better supported in other ways, too. Users no longer have to manually create and delete folders. In a nod to iOS, the new home screen will automatically make a folder when one icon is dragged on top of another. When the contents of a folder are dragged out and it only has one item left inside, the folder will disappear and revert to a regular application launcher.

Folders on the home screen look like translucent circles that contain a stack of icons. When you tap the folder, it expands to show a grid of the icons inside. The folder can be closed by tapping outside the grid. You can now long-press and drag to change the order of the icons in the grid—another nice feature that wasn't available in previous versions.

A new search box stays permanently mounted at the top of the home screen, just below the notification bar. This box replaces the traditional home screen search widget. Although it is designed to look like a text box, it's really just a launcher that activates the platform's built-in global search application. The global search will display suggested completions, including popular Google queries, as you type.

You can use the tool to perform a Web search or search for content and applications on the device. Like its predecessor, the search tool lets you configure which sources you would like to search. In the screenshot above, you can see it identifying an application, a book in my Kindle library, a contact, and an Evernote notebook.

Navigation buttons

At the very bottom of the screen, a special area is reserved for the standard platform buttons. It is displayed persistently, not just when the user is viewing the home screen. This area replaces Android's traditional hardware buttons. By default, it has buttons for activating the platform's "back" and "home" features. It also introduces a new button specifically for invoking the task list.

The traditional search button has been dropped entirely, and the menu button is being gradually phased out. Applications are now supposed to expose their menu options through a special title bar button. When the user runs third-party applications that haven't been updated to conform with Android 4 platform conventions yet, a menu button will appear in the bottom area.

The new navigation buttons will rotate when the user flips the phone into landscape orientation. They will also dim into small white dots when the user is running certain full-screen applications, such as a video player. I was hoping that Google would use the on-screen navigation buttons as an opportunity to introduce some cool multitouch gesture features in that dedicated screen region, but no such luck.

Launcher and widgets

The ICS launcher is inherited from Honeycomb, but it has been scaled down to fit on a phone-sized screen. The applications are organized in a grid across pages that can be navigated by swiping horizontally. This is a major change from Gingerbread, where it was possible to scroll vertically through the entire list.

Another feature inherited from Honeycomb is the inclusion of widgets in the launcher interface. As the user swipes through the pages of the launcher, it will show available widgets after the user reaches the end of the application list. There are also tabs at the top for quickly jumping to applications or widgets.

The way that ICS tacks the widget library to the end of the application list will probably make third-party widgets more discoverable, but it could also confuse some users. It's a little disorienting when you are flipping through your application list for the first time and suddenly hit a page with a tiny analog clock and a stack of books. This behavior is really unnecessary anyway, because the tabs at the top already provide adequately convenient access to widgets in the launcher.

When the user performs a long press on an item in the launcher, the launcher interface will disappear and the user will see a zoomed-out view of their home screen pages with grid markers. This makes it really easy to drop an icon or widget in the desired location across all of the home screen pages. While the user is dragging the icon, an "uninstall" action target will be shown at the top of the screen. If the user drops an application icon on that target, the application will be removed from the device.

Android 4 has also inherited Honeycomb's support for resizing widgets. Unlike some of the third-party home screen implementations, however, the new stock home screen won't automatically make all widgets resizeable. A widget can only be resized if it was designed to support the feature. Performing a long-press on a resizeable widget will cause the scaling knobs to appear, and they can be dragged to set the size.