I use it all the time to find great stuff. I still listen to stuff from my own library a lot, but Pandora is a great way to mix it up, AND to discover new stuff (or stuff you like that you may have forgotten about).

In the past week, I've bookmarked about 10 songs from Pandora that I intend to purchase, just by listening to Pandora-created playlists based on two of my favorite artists.