I've been playing the game for about a week and a half now so I've deffinitely had a chance to spend a decent amount of time with the game. I actually would have beaten the game days ago but I got incredibily sick and then went on a trip to Montana so that put a hinderance on my progression with the game.
Man, there is a lot to say about Darksiders so feel free to ask away if you have any questions, but the short of it is that it's a crazy fun game! Though it borrows mechanics and concepts from Zelda, Gow of War, and Devil May Cry it still manages to stand on its own as a game (which is key) and be incredibily fun. But I think the problem with some people might have to be their perspective (or lack thereof) going into the game with false expectations--they might be expecting Darksiders to be one of the games I listed above when it's not. Again, Darksiders manages to stand on it's own and feel mostly unique. One thing it most certainly is is an action/adventure game with heavy comic book influence, and I mean that in terms of asthetics, storytelling and overall design. I think it works really well for Darksiders because you can tell that Vigil set out to do this from the outset.
All the dungeons are exciting to play. If I recall correctly there are 4 or 5 of them and I'm currently on the last dungeon of the game, which I think the design is top notch. It's unique in concept, well thought out, makes you stop and think every once in a while and most importantly is fun to play.
If you want more info check my Twitter feed where I was Tweeting my thoughts on the game as I played it.
http://www.twitter.com/heymarkd
Oh, and riding Ruin (the horse) feels incredibly awesome.
Note: One last thing--the game doesnt really get going until about 1.5 hours into the game.