I recently learned that my phone, Samsung Moment via Sprint, had an update that allowed the phone to use Android 2.1 from 1.6. Like reinstalling windows, it feels like a brand new phone again.
The alarm clock gained the ability to hide the clock, which provides more room to see what alarms one has. The phone's basic lock gained a slider to open, making unlocking while in a pocket much less likely then power -> menu click was. A basic widget for one touch toggling of wireless, bluetooth, gps, app syncing, and brightness was added. Convenience of magnitudes.
Alas, the OS update came with a glaring mistake that strongly shows me the developers for the software live in large cities. The signal strength meter is optimistic instead of pessimistic. If the phone doesn't know the current signal strength is, it defaults to full bars. This gives false information, and is annoying.
As I've only seen Android 2.1 on a Sprint phone with their brew, it may be Sprint trying to make themselves look better. If you have another service, I'd like to know if you are witnessing the same or not, and which version your using.