For me, Grim Dawn was a good game and a good alternative to Diablo 3. Its done very well by arpg standards, and its still different enough from Diablo 3, which makes it somehow fresh and interesting. Its done by a small indie team, which explains the not up to date graphics and the lack of a multiplayer infrastructure, but for me, as a single player, that is fine.
Right now, i'm at 65 hours played, which is fine for a 20$ game, so it feels like a good investment.
Would i play it for hundreds of hours and dive really deep into endgame? Probably not. The first play through in veteran mode was not too easy and not frustrating, that was quite good. Now in my second play through in elite mode. Progress has become a lot slower. Difficulty spikes between "boring, everything just takes long" and "corpserunning 15 times on a single enemy". Progress by loot is very random. It feels like d3 vanilla, almost everything i find is crap and the good stuff doesn't match my class. The bounty system is like diablo's in very very unpolished. When i was 15 years old and had so much free time after school, i would have played this for hundreds of hours. Sadly, my free time these days is much more limited, so i will probably not finish the game on ultimate.