Aside from sheer speed improvements, there are few other obvious changes. The home screen has been changed a tiny little bit. At the bottom of the screen, the button that would normally be used to access the main menu has been joined by two more buttons, each useful to have on-hand (or, under-thumb). To the left is a button that brings up the phone program, and to the right is a button that brings up the web browser. Having access to these two extra programs from each of the five home screens is a really nice touch.
Perhaps the single biggest new feature is the built-in support for tethering and Wi-Fi hotspots. These tools worked flawlessly, allowing me to turn T-Mobile's 3G network into an instant internet connection for my laptop and other Wi-Fi enabled devices. It is simple to use, and just works. Turn it on, find the AP, connect, and you're good. Well done on this, Google.
What has to be the most-asked-for new feature has to do with the Android Market. Google has revised the way it works so that users can update all of their applications at once. Rather than painfully updating them one at a time, users can update in one fell swoop. What's more, if users wish, they can set it so that applications update automatically.
Other nifty features include a native task killer. This is a solid addition. Previously, users had to wander around the Android Market looking for task managers. I never found one with which I was satisfied. Now that Google is offering one, I won't need to bother.
Last, Android 2.2 Froyo comes with Flash Player 10.1 baked into the browser. That means a whole new world of web content is available to consumer. It isn't a perfect experience, but it works pretty well.
In all, Android 2.2 is a great improvement for the Android platform, and a clear step ahead of many of Google's competitors. Research In Motion, Microsoft, Nokia, and Palm all have a lot of work to do if they wish to remain competitive with Google and its Android army.