I use iTunes on Windows to play music at work, and I have a lot of songs (> 4000). Songs I really like I rate five-stars, and I use Party Shuffle with "play higher rated songs more often" turned on. But still, I hear a lot of one-star songs. And looking at the number of times each song has been played, it turns out there are over a thousand songs that have not been played at all, while many have been played over ten times, even though I haven't rated them highly.
So I made a smart playlist with live updating called "Least recently played", limited to 2500 songs selected by least recently played. Then I run Party Shuffle off of that playlist. Now it feels like I'm listening to a whole new library of music. I had also tried a list called "Not one star" which selected based on the rating not being one star. That was to permanently exclude songs that I had marked with one star. Next time I fiddle with the playlists, maybe I'll try combining them.
For lots more ideas of how to use smart playlists, take a look at SmartPlaylists.com. The people who post their ideas there have a whole lot more energy than me for making their music libraries dance.