Mixed bag this one, at launch it was unplayable, the flickering, artifacting and pop in, mixed with all the other problems like mouse acceleration, low FOV made it a total mess.
Once the visuals were fixed with a patch and new beta drivers, and the other variables tweaked with console commands, the game for me has been really fun so far, about 8 hours worth I guess.
It's a game that looks really good as long as you stay about 20ft away from any surface, but what it lacks in texture detail it does make up for in unique art assets. It's the first time I've ever seen anything quite like it, and it's quite eerie, you don't get the usual repetition in textures and meshes, which makes the environment so much more believeable.
Mixed with high resolution textures the engine could make something truly spectacular, I was hoping that a corridor crawler like Doom3 could put the same 20Gb texture limit towards some really high definition areas and get a truly fantastic looking game, but it seems like Doom4 is on hold.