I was just about to pay for slacker but decided to get some opinions first.
I use the free service and really like it, they gave us Premium free for a month and it was great, seems the sound quality was better and you have more control. I have unlimited data so the station caching doesn't matter, but it could be useful if you are limited. Check out the Slacker Forums to see who complains about what.
You can check out Google Play Music for a month for free and see if you like it, only read good things about it. I use the free service, it uploaded 3,000 songs for free so far and I still can put up more, and I share it with my wife's phone. You can see if you like Pandora, not sure of their pricing, or Spotify, they both offer artist and album when you pay.
Iheart radio if there is/are particular station(s) that you want to listen to. Especially from different markets(if you travel)
If you like I Heart Radio then you'll probably love http://www.radiosure.com/ - free radio player. It comes pre-loaded with about 15,000 radio stations from all over the world - and you can record any of them.