Current CVS contains a lot of code cleanups which aren't too well tested. Seems to be working with me, but I'm still a bit worried I left some very nasty bug lying around somewhere. There's anyway been many nasty fixes since 0.99.4, most importantly with mbox handling and SEARCH command.
I've also added support for SORT extension. It's not very fast currently, but it should work. I tested with squirrelmail and it looked fine. So, those people wanting to use Dovecot with webmail might try it now. :) THREAD extension is still missing though.
So, here's a 0.99.5 release candidate 1. I wouldn't recommend it for production usage yet, but I'd hope some people to test it before I'll put out a real release. Just so that I won't be (again) releasing n+3 versions in a few days :) You can get the sources from http://dovecot.procontrol.fi/rc/
I'm going away for christmas tomorrow, once I get back I'll do some more testing and auditing and get the final release out. Next weekend probably.