There isn’t anything mentioned in the API differences or anywhere that I can find so far, on changes made to the underlying skin of the RatingBar component.
If you have a rating bar in your 2.2 project using Widget.RatingBar.Small as a parent for your custom skin, you’ll most likely see a weird background skin now surrounding your rating bar. This could be the AbsSeekBar or ProgressBar, but to me it looks like a ToggleButton. Regardless, it’s not your desired look and here’s how to get rid of it. Just remove the .Small from Widget.RatingBar.Small and make sure you have set min/max heights for your stars so they shrink or grow to your desired size.
ps. I’ll get an example once I get a good enough plugin that doesn’t crash my wordpress when I drop some XML in it. 🙂