Anyway, last week I downloaded the Last.fm player on my computer and my iPhone. It automatically imported my music list from my iTunes library. I clicked on "recommended" and listened all day long. The program selected songs it thought I would enjoy based on music already in my library. There was no interruption. It did not play any songs from my library. Over the course of about seven hours there was one song I skipped because I didn't like it. And there were dozens of songs and artists I'd never heard before that I want to hear again. As each song plays, the CD cover is displayed with information about it and the opportunity to click to purchase--really brilliant marketing. There are also channels by genre and probably more options to discover. I haven't explored all the features.
The sound quality was great. Again, over the course of about seven hours there were a couple of hiccups, but they were just flickers. I have a first generation iPhone so I have to have high speed wireless access (no G3 for me, yet), but when I have a wi-fi connection, it works great.