I know something similar has been suggested in another post, but I'd like to second it and add my own twist.
Before I had my BB, I used iPod+iTunes for podcasts (and audiobooks, music). I love the "smart playlists" in iTunes, and I'm glad Podtrapper now meets most of that functionality with the auto-add and sort in 1.8.x. I'd like to see the ability to have multiple playlists, with each playlist able to have its own auto-add and sort criteria, and episodes automatically added and removed from all matching playlists.
I'd also like to see more criteria for selecting and sorting episodes. For example:
-Year (to easily differentiate new episodes from podcast archives I'm working my way through)
-Podcast name or by feed
Right now I can accomplish some of this with the playback priority, by lowering the priority of the podcasts that I'm working through. However, this puts new episodes from those podcasts at the very bottom of my playlist, and every once in a while I'll have to listen to those manually so they don't pile up.