Just a simple question:
How does amarok 2 reads the covers? I've the covers embedded in the id3tag and in the respective album folder (not named cover/front.jpg or something like that), but also have some dirs with artists with just one song (cover embedded too). All covers are 300x300, but amarok always shows an upscaled version of a thumbnail (50x50 I guess), which is pretty ugly.  On the artist with just one track amarok shows up the same image for every artist/album, even in the collection. When I click "Show cover" the correct scaled cover is shown. So do I have to remove the covers from the folders to get the embeded images initally?

Embedded covers are (not yet) supported in A2 I think, but I'm not fully sure about this...

I notice someone on the list opened a bug for something that sounds the same as your thumbnail issue... worth checking.
http://bugs.kde.org/show_bug.cgi?id=181770