I'm using it for two months now. At first, you get a trial to test their premium service ( blocks ads, lowers traffic etc. ) and after that, it's .. well, i din't notice any differences.
I used mostly Pandora, tested Beats, watched Netflix etc.. It's pretty reliable, as long as you have a good network connection. It's set to on demand after you installed their profile which I turned off because it was quite annoying and sometimes the iPhone couldn't establish a connection. But this was most certainly because of bad reception when I was "on the road"
It's one of the best services so far, been testing several ones. No one was perfect, either connection problems or unstable connection / bad speed etc.
Spotflux is my top rated at the moment, simply because it's free/extremely cheap and offers everything I need without limitation.
And as I mentioned above, the trial's a month of premium subscription.
Good luck and best regards.