There are no set 'stations'. Everything is custom for you. If you get a song that you dislike, give it a thumbs down. Then, give the songs you like a thumbs up. Over time you're library will expand as they learn more about your musical tastes.
I have a station I've been using for two years now, and it's near perfect. I almost always hear a great band I've never heard before, and all the classics play as well.
Yeah, for example, I started off with a Red Hot Chili Peppers station a couple years ago, and morphed it into a station based on exactly what I like - harder modern rock like radiohead, audioslave, franz ferdinand, foo fighters, and rage against the machines, and lighter stuff like death cab for cutie, red hot chili peppers, the killers, the raconteurs, nirvana, and tom petty. It's dead on with what I enjoy listening to, but only because of how I rated the songs (with thumbs up or thumbs down, or even if I tell it not to play for a month)...
And that's just the modern rock station I created! I have another three great stations - a dedicated rap station, a ded. reggae station, and a great classic rock station.
I have to admit, even before pandora created an iphone app, I loved them and what they stood for (I'm all about open-source and the music genome project. In fact, if I didn't own a mbp, I'd probably have a dedicated system running linux!). Now, because of the app, I just love them even more!
Justin