It's known just about everybody i put in there, Rush (although it's not _as_ usefull in that case, their music is great, but it's the lyrics and memes that really make them something special) Evanescence, Faith and the Muse, and Heather Alexander.
It couldn't find Aikawa Nanase or Nobuo Uematsu, which didn't suprise me up until i found out that it has "Final Fantasy," "Game Music," "Manga," and "Yasunori Mitsuda." Strangely, the Final Fantasy discography is empty, but they have Final Fantasy CDs listed for Game Music :)
I think the links to amazon are a smart idea, but they'd probably get even better results if they linked to iTunes samples or something similar as well. If i'm actually looking for someone new i'll probably want to hear something from them before buying it, and if i wander off to find a sample it's unlikely that i'll remember/care enough to come back to the site later to get them credit with amazon. (For that matter, i'd probably go to BarnesAndNoble.com instead so i could avoid giving amazon money.)
It's fun to just roam around and see what you find. I've found some interesting sounding bands, and currently i'm trying to figure out how to get from The Beatles (the biggest dot i've seen so far) to Rush. It's more difficult than it sounds, because the links aren't all bidirectional. You can get to The Beatles straight from Rush, but not many groups show Rush in return.