I agree with lyonzy
I just converted two phpBB2 forums to phpBB3 and the convertor works well, the resulting phpBB3 forums look pretty slick I must say (it does help to have a friendly and efficient host - they bailed me out twice during the process!!)
but It's only when you begin posting and looking at the way phpBB3 works, by having a working phpBB3 forum, that you actually begin to see the work that has gone into the new version
there are many good features that have been included and these become apparent as your new forum moves along day to day
Congratulations to the people behind phpBB3, at one time it seemed like it was taking forever to get a Gold Release but now it's happened :WELL DONE!!