It's basically a Diablo clone, and in this case that certainly isn't a bad thing. It's literally what Diablo3 should have been. In-depth skill trees, nice graphics and great dungeon crawl gameplay.
Heretic and I have spent the last two days smashing the everloving shit out of it. It's had a few stability issues (it is open beta after all); but they are active in sorting out the bugs.
It's free to play and uses the micro-transaction model. The major difference is it is NOT pay 2 win.