What does Android 2.2.1 bring? Compared to 2.2, what does 2.2.1 bring that's new please?

Thank you.
I'm not aware of an official changelog anywhere, but you can look at the commit log on the git repository here. Anything between the 2.2_r1.3 tag and the 2.2.1_r1 tag was a change added in 2.2.1.

The summary: it's basically just bugfixes, hence why it's a smaller increment (as opposed to 2.2-&gt;2.3, for example).

Note: If you're getting a 2.2.1 update from a carrier then they may have added other changes to their own software, so the above applies to the Android OS itself and not any additional components.