It's taken a year and a half, but I have reached a milestone here at work.
After 18 months of listening to iTunes and rating every song, I now have a library of nearly 3,500 songs that are all 4 or 5 stars in my not so humble opinion. I've culled the rest of the herd (from my work library anyway, I keep the 3 stars at home).
Of course, I complete this little project just as Genius becomes available and somewhat renders my library of nothing but awesome songs less relevant.
In the past I've tried Pandora and Last.fm. I like them both, a lot. It's a great way to discover new music. But they both tend to get a bit repetitive after a solid week or so of listening. That's not a viable long term solution for me. Also, I worry about bandwidth issues here at work. If I can create a “My Top Rated” playlist that's 11 days long, I probably should. If we get several people streaming Pandora on the campus network, it would probably start to present some congestion issues. So I'll do my part to conserve a limited resource. :)