I found another bug or possible improvement in the latest beta (and probably versions before that).
When you insert a CD into your drive and open Picard while the Disk is still process of loading the whole UI doesn’t respond and only gets accessible until after the loading has ended.
This only happens on startup. If Picard is already opened and I insert a CD the UI keeps responding. The only part that gets a bit unresponsive during insertion seems to be the lookup dialog, which doesn’t open till the disk is properly loaded. But that is to be expected, I guess.
All in all I think this isn’t critical at all, so you might change the issue type from "Bug" to "Improvement".