I've upgraded to Raring on both my machines, and I'm loving it. The UI tweaks are minor, but they improve consistency in little ways, and the system seems just as stable as ever. I don't really see any drawbacks and haven't hit any regressions. I haven't noticed a lot of real improvements, either - it's just another edition - but getting more recent software overall seems at least worth the trouble of upgrading, on balance.
I know I shouldn't use tildes for decoration, but they always make me feel at home~