I really like my iPod Nano (I know, everybody does). One thing I like about it is the rating system, which I'm using to figure out what music I really like. I started with around 980 songs, chosen fairly quickly from the 8000 or so on my home PC. So this was my "optimization starting point," hardly random to begin with, but subject to further "selection pressure" from the 5-star rating system. I rate the songs and remove the "weak" ones each week to make room for new music.
Starting from the bottom, I use one star to mean "delete" (next time I'm in iTunes). Two stars is a song that's OK and I might like to hear occasionally, though I might delete it if I need the space. Three is a good song that I'm happy to hear occasionally. Four stars is a really good song that I'm ready to hear any time, and five is basically the same, but also "undeniable" (truly awesome, classic, or both - or one of my own songs, some of which are fives to me at least!). I usually apply these ratings while listening, basically the only "input" allowed while listening to a song on the iPod (I can edit general information or delete songs only when plugged into a PC with iTunes).
With this system, I've so far rated 411 of the 977 songs currently on the iPod, with 131 of those getting five stars (copy/paste into Excel helps with this vital analysis). Some of my five star artists are Aimee Mann, Badfinger, Bare Naked Ladies, the Beatles, Billy Joel, and Bright Eyes. Scrolling to the end of the fives, I see Simon & Garfunkel, Sir Neville Marriner (for a Mozart piece), Stevie Wonder, Sting, Trisha Yearwood, U2, and Van Morrison.
Just thought you'd want to know. OK, you didn't, but I did.