Just hit 22 this morning, and yeah, this game is actually really solid. Probably the best mobile game I've played personally, though I AM playing on PC, lol. Sure, some of the monetization CAN be pretty abrasive, but you can also just not dabble in that whatsoever. The game doesn't force you to pay to proceed or anything remotely similar from what I've seen thus far.
So, if you have any kind of self control, you won't have any issue here whatsoever.
If you're hopeful and hyped about Diablo IV, this is a nice inbetweener until then. I'd recommend giving it a shot, I mean, it's free, why not?