It fixes a lot of bugs and improves stability significantly. I strongly recommend that everyone update to 2.2 as soon as it is available.
Some major bug fixes include:
1. Timestamps - While the 2.1 update claimed to fix this, it didn't. This time I had users from the UK and the east coast of the US help me out and confirm that they are actually correct now.
2. Chat now allows you to go offline or back online if you have chosen to go offline from the web. This should resolve the problem many users experienced where they were not able to send chat messages.
3. Duplicate friends should no longer appear. The 2.1 update also claimed to fix this and didn't, but I have put in place a much better solution this time.
4. Notifications - for many users the app crashed when tapping the notifications tab. This has been fixed, and also the appearance of the Notifications tab has been fixed so it includes all of the details again.
5. After deleting messages from the Inbox, they will no longer come back when you restart the app.
6. The Quotes section of profiles will no longer bug out when the quotes were really really long.
7. Hitting "See All" in the photo browser should no longer cause the app to crash so frequently.
8. The photo viewer is much less flaky, so it is not as easy to accidentally tag a photo.