One really annoying bug exists in iTunes 10.1.1 (4). When you buy a track from the iTunes Store, it doesn’t go into Apple’s default ‘Recently Added’ smart playlist. This makes it so you have basically two different ‘inboxes’ for new songs, podcasts, etc. You need to remember whether you bought a song on iTunes, ripped it from a CD, or downloaded it as a free podcast, etc.
It would be better if songs you purchased appeared in ‘Recently Added’ along with everything else. It would be especially useful when traveling and listening to previously-downloaded podcasts.