First and foremost, the bottom panel of Android 2.2 is gaining two incredibly useful soft buttons. Before, there was just a simple multi-screen button at the bottom of Android 2.1 which brought up your entire grid of installed applications. Now, that button is flanked on the left by a Phone shortcut (brings up the dial pad for making calls) and on the right by a Browser icon (which opens up a Web browser). HTC provided similar shortcuts already to those with Sense-enabled Android phones, but users of "stock" Android (namely Nexus One owners) will be glad to see these two soft buttons added. It was kind of silly to require users to hunt for their Phone app at all; this is a mobile phone, after all!
Outside of that, most of the cosmetics are the same. The fonts are the same, the icons are the same and the backgrounds are the same. You'll find a small design tweak here and there, but mostly things are the same as what you would find in 2.1. That's not a bad thing; Google has a good thing going with design, and there's hardly a reason to reinvent the wheel when something's working out well.
The most noticeable change in 2.2 compared to 2.1 is the overall speed of everything that you do within the mobile OS. Yes, everything. Google has placed a heavy emphasis on making Android 2.2 run lighter and faster, taking better advantage of the hardware already available on the market. In other words, there's no need to buy a smartphone with a faster CPU in order to see performance increases in Android; 2.2 comes with a Dalvik VM Just-in-Time (JIT) Compiler, which results is 2x-5x faster performance over 2.1. Even in graphically intense apps, you'll see stronger frame rates and smoother gameplay. We tested out a number of our more intense applications, and we definitely noticed increased performance compared to our old 2.1 build. Things simply felt more nimble and less burdened. It's a tweak that will probably not get the credit it deserves being that it's mostly behind the scenes, but 2.2 brings a definite increase in speed--one's that much, much appreciated.
Another subtle, albeit excellent, change in Android 2.2 is a new push service that allows select applications to receive instructions via a Web browser. This allows users to do things like search for directions on their home PC before heading out, and then clicking a single button in a browser task bar to have those exact instructions sent to the phone. This is far easier than jotting down an address and attempting to re-enter it manually within Google Maps once you've left the house. We suspect that integration with Google Maps is just the beginning for this feature. Imagine being able to call a friend and have them push directions to their house directly to you, or being able to push airline tickets, concert tickets, etc. to your phone's display before heading out.
Android 2.2 is also bringing about a number of Settings options that will make everyone's life a little bit easier. There's now a setting for backing up your applications and restoring that information upon re-installation. Potentially more interesting is the native ability to store applications on an SD/microSD card. This is a huge, huge change. One of the main gripes against Android was that users could only install applications onto the free storage that was built into one's phone. No SD card loading was allowed, so if your Android handset only had 100MB of internal storage space left open, you couldn't have more than 100MB of apps installed at a time. If you wanted more, you had to delete some of what you had already installed. Apple's iPhone has at least 8GB of internal storage, and you can fill all of that with apps if you so choose.
With this new "Move To SD" feature, users can manage applications and move them to and from the external storage card with a single click. Of note, applications will have to support this feature, so not every single app will be able to be stored externally. Developers can choose to only allow internal installations if they feel that the latency issue of fetching content on an external SD card will provide exceptionally poor app performance. We doubt too many devs will enforce this, though. This new rule also means that you can have several SD cards with different batches of apps; one card for work apps, another for personal. It's like carrying multiple phone profiles by carrying multiple cards.
Another major, major addition to the framework of Android 2.2 is the addition of Portable Wi-Fi Hotspot. This feature does exactly what you think it does: it enables your Android phone to turn into a mobile Wi-Fi hotspot, exactly like Verizon's Palm Pre Plus and many other phones can do today. Basically, with this enabled, your phone connects to a data network and then broadcasts that signal out via Wi-Fi. A handful of devices can then connect to your phone in order to connect to the Internet via AT&T or T-Mobile (based on what SIM you have inserted). Very few mobile operating systems ship with a native ability to tether at all (2.2 adds USB tethering), let alone tether via mobile hotspot. For travelers, this is a huge addition that's impossible to overlook or take lightly.
Within the App Market, two changes are being made. They are changes that should have been made a good while ago, but we'll say that late is still better than never here. In Android 2.1, the only way to update an app is to do so manually, and you have to update every single app manually. In 2.2, the option to Automatically Update when a new update is pushed out has been added, as well as an Update All option that will bring every app in your phone up to date rather than forcing you to press "update" for every last app. A big time saver, that's for sure. Users will also now be able to catalog and send "freeze reports" to developers in order to let them know exactly what went wrong and what the circumstances were if and when an app crashes. This should help devs troubleshoot their apps and push out more stable releases in a shorter amount of time.
Okay, this one's big: Flash 10.1. Yes, this is the first Android version with native support for Adobe's Flash within the browser, which means that you can finally surf to Flash-enabled Websites without any errors popping up. This is something that Apple's iOS will probably never support, at least not for the foreseeable future. Performance is obviously dependent on what phone you have (and the hardware within), but at least support is here. Once phone hardware evolves another generation or two, most Flash-enabled Websites should play back without a hitch.
There are a few minor graphical changes within a few frequently used apps; Gmail labels are now easier to sort, Google Calendar now has an easier-to-navigate user interface, the screen lock can be set to PIN versus code swipe, the car dock user interface has been tweaked to better suit car input, the camera has more streamlined controls and the voice recognition settings allow for users to select their nationality in order to better recognize accents. All in all, we're looking at a hefty stack of changes for a "mere" point release, and that Flash 10.1 addition will loom large for generations to come. The iPhone 4 can't load Flash websites due to Apple's restrictions, but Android 2.2 will let even the Nexus One do just that. We won't comment on how the fanboy wars will go in this particular discussion...