I picked it up during the sale and put about 10 hours in.
Holy shit is it a letdown. It's basically TQ with a new skin with all the problems, slog and boredom packed in. Where all the other grindfests try to switch it up, Grim Dawn just buckles down and throws more of the same on your head. Would you like an extra pack of undead thrown on your head randomly ? Here are 2 extra floors of this dungeon offering fuckall interesting ! Non-randomized world that takes zero advantage of that. Quests that are slog to find and do. Character creation that is the most boring at the start. Skill points that give you only stats (PoE avoids this by having all the actives easy to change) Death system that punishes you for not dropping a portal ever 10 steps, equivalent of quicksave spam. To even put this game on a similar level as PoE and D3 is an insult to both.
The good points so far are the constelation system (although I have a feeling you can't respec that, effectively fucking your character ?) and choices during quests, although I have no clue if they actually change anything. The way you can rebuild parts of the world so far seem neat, but again no clue if it really changes anything.