If it is getting info from genere, year, ect it might be a good time to update your ID3 tags. For those of you that don't keep an organized collection I don't envy that task.
I quite like it, once 2.1 comes out for the iPhone I will be finding a song and making a genius list on the fly instead of always being on shuffle with it.
It works pretty well. What I like is that it takes the songs you don't listen to that much from albums and put them in the playlist so they fit nicely in there. I've find it works really well with endings and starts. If a song ends abruptly, the next song is usually building up its intro. If it ends slowly, the next song can be instantly fast. I really really like this. I don't see how it will become more clever by user submissions though. I think the intelligence thing only applies to the recommendations you get from the iTunes store
So far I've been really impressed. It definitely doesn't go just on genre or date. Should be only a matter of time before the process is out in the open.