I've enjoyed Pandora, and discovered a lot of music because of it. That's more what I used it for was hints around other genres that I might like. I started out with a Maceo Parker channel because I liked funk/jazz music but could not remember more than a handful of mainstream artists. That channel alone sparked a heap of music surfing and a boost to my CD collection. I did participate in the grading and it did end up venturing well out of those genres. It ended up leading into a lot of hard bop and other jazz milestones.
Spyro Gyra station is another that ended up being a long and ongoing music journey. It may be considered mainstream, but not so much when you figure jazz makes up only about 4% of the music audience.
Just checked and it still works for me and all of my stations are still intact. Also tune into it with the echo dot from work.