I see that MySQL 5.5.21 has just been released. This sounds interesting. I’m mainly running 5.5.16 which has been broadly stable, but I have been caught by a few important issues which 5.5.21 fixes according to the change list:
These together with a few earlier fixes after 5.5.16 are certainly interesting to me, so I’m eager to try out 5.5.21 and see how it fairs.