I must have better luck with it, because Pandora has introduced me to a lot of really good stuff. I usually just listen to it when I'm in a "shuffle" sort of mode and not really set on one artist/album at the moment. I've also found a lot of songs I had forgotten about. Thinking about upgrading to Pandora One and I wish the skip limit would be increased, but that's just about my only gripe. Never heard of Songza. May have to check that one out.
I've definitely found some incredible stuff through Pandora. Pandora introduced me to Boyd Rice and AIDS Wolf. A lot of good black metal, too, maybe even Burzum, I don't remember.
But the thing for me is, my taste is exceedingly idiosyncratic. I love Pantera but I don't want to hear one note from White Zombie or Machine Head. I love 2Pac but I don't want to hear any Biggie or Nas. The way Pandora works is by putting together artists in the same ilk, Pantera with White Zombie, 2Pac with Biggie... so it's absolutely brilliant for introducing anyone to a new genre they've not yet explored the basics of. And it does have some good deep cuts too. But it's only palatable for me when I'm okay with listening to a whole genre without too many stipulations.
Songza is really awesome. Right now i'm listening to a Songza station of nothing but
acoustic versions of pop songs. As an avowed lover of Unplugged this is a pretty incredible station for me. This forum itself also
has its own Songza station!
I love Last.FM but for radio it's no match for Pandora. Their catalog is way limited as far as playable tracks go. It's more for keeping track of your catalog and listening habits imo.