I couldn't agree more. Slacker.com blows Pandora out of the water, it's not even close.Slacker Radio is my new favorite. Pandora has been removed from my iPhone now. The main advantage it has over Pandora is that it already has preset stations for different music tastes. You can still create your own station just like on Pandora.
The customization of the stations logic when you create your own is great too. As are the pre-made stations that actually list what bands are played on it (as mentioned by CTHP). Highly recommend it.