One of the iOS platform's advantages over its competitors is that official software updates are not just provided to older devices, but provided in a timely manner on a single date. It gives older phones and tablets a nice longevity boost, and allows Apple to continue selling older hardware that works and acts much like its newer counterparts.

The downside of that approach is that only Apple gets to decide if your hardware is worthy of an update. This can cause two problems: the first is that owners of not-so-old devices can be left with old software, as is happening to owners of the original iPad (which was, believe it or not, still the newest iPad available just 18 months ago). The second is that an update can be pushed out to devices that aren't ready to handle it, as happened when the iPhone 3G received the iOS 4.0 update in 2010.

That update wasn't just missing features compared to the version of iOS 4.0 that shipped for the iPhone 4 and iPhone 3GS—it also made previously existing functionality much slower. Now iOS 6 is here, and the iPhone 3GS is in a similar position: it has just come off the market, and it's using less RAM and a slower processor than the other supported devices. Does iOS 6 make the iPhone 3GS an unusable mess, or can people with older phones perform the update without reservations?

What don't you get?

Apple has been restricting certain iOS features to certain devices since iOS 4, and iOS 6 is probably the most confusing example of this yet, mostly because there are now many different iOS products with varying performance levels.

As the oldest supported device, the 3GS misses out on the largest number of features: it can't use the 3D Flyover or turn-by-turn navigation features of the new Maps app (restricted to the iPhone 4S and newer), Panorama mode (iPhone 4S or newer), or the offline reading list feature (iPhone 4 or newer). Features from older iOS versions that didn't make it to the 3GS are still not present in iOS 6: these include location-based Reminders (iPhone 4 and newer), WiFi Personal Hotspot (iPhone 4 and newer), FaceTime (iPhone 4 and newer), AirPlay Mirroring (4S and newer) and Siri (iPhone 4S and newer).

These missing features generally don't change the operation of the phone—they're simply not present. One app that does change is Maps: on newer devices, getting directions from "current location" invokes the turn-by-turn navigation feature. There's also a button in the lower-left corner of the screen that you can tap to bring up all the steps in your route.

On the 3GS, getting directions from your current location brings up a list of driving directions that you can swipe through to see where you're going—swiping from the left brings up the next step, and swiping from the right brings up the previous one. There's also no button to tap to bring up all of the steps at once, which seems like an odd omission to me. (If you have a newer phone and would like to see how this works, you get the same interface if you use anything other than "current location" as your starting point when getting directions.)

Otherwise, Maps on the 3GS brings all of the changes it features on newer phones, including Yelp reviews, the revamped interface, and the lack of integrated public transit directions.

What do you get, and how fast is it?

Aside from the growing list of features restricted only to newer phones, the iPhone 3GS actually gets most of the new OS's tweaks and refinements—iOS 4 set expectations low on the iPhone 3G by excluding some of that version's best improvements, so it's nice to see the older handset so well-supported in this case. With the exception of the Siri and Maps sections, just about everything mentioned in our main iOS 6 review applies to the 3GS, including Passbook support, Facebook integration, shared Photo Streams, revamped sharing menus, Do Not Disturb, iCloud Tabs in Safari, the new Find My iPhone tweaks, the Camera app's exposure lock, the new Mail features, and the new call features, among others.

The new features also don't slow the phone down appreciably. To give you some idea of performance relative to iOS 5.1.1, we launched some standard apps in both versions to measure application launch times. These numbers measure the number of seconds starting from when the app icon is tapped and ending when it becomes usable:

Application iOS 5.1.1 iOS 6.0 Safari 1.3 seconds 1.4 seconds Camera 2.0 seconds 2.3 seconds Settings 1.8 seconds 1.7 seconds Mail 1.3 seconds 2.1 seconds Messages 2.4 seconds 2.4 seconds Calendar 1.4 seconds 1.6 seconds Phone 1.1 seconds 1.0 seconds

Most of the results are well within the margin of error, with the exception of Mail, which consistently took around an extra second to launch. In practice, the phone feels about the same as it did running iOS 5—occasional stuttering and nowhere near as snappy as my current 4S, but still responsive to input in a way that the iPhone 3G with iOS 4 was not.

We also ran our standard suite of smartphone benchmarks on the 3GS under both iOS 5.1.1 and iOS 6 to see if there were any improvements or regressions. While GLBenchmark and Geekbench scores remain unchanged from iOS 5, improvements made to Safari's JavaScript engine continue to benefit the 3GS just as they benefit newer models.

While iOS 6 doesn't slow the 3GS down compared to iOS 5, the phone is still getting pretty long in the tooth—three years is a long time in technology. That goes doubly for the smartphone and tablet industries, where a doubling of performance between product generations is still possible.

Conclusions

Even if you subscribe to the belief that each year's iPhone improvements are merely incremental (and I tend to upgrade my phone hardware once every two years, myself), the jump in performance and features that you get by moving two or three generations at once really add up to a substantially better experience.

iOS 6 doesn't make the iPhone 3GS any slower or more difficult to use than it was before, which should be good news to anyone who keeps theirs around as a secondary or backup phone—indeed, it's pleasantly surprising how many of the refinements and improvements make their way down to Apple's oldest-supported piece of iOS hardware. However, that hardware has been surpassed so thoroughly by other iOS and Android handsets at this point that it's difficult to recommend it as a primary handset. You don't have much to lose if you upgrade a 3GS to iOS 6, but there's a lot more to gain by investing in a newer device.