According to critics: very.
According to my 17 hrs of play so far on it....not one bug other than my crow (Dust) disappearing one time.
This game, by the way, as a follow up regarding my opinion...
...is AWESOME. If Darksiders was Ocarina of Time, this is Majora's Mask. If Darksiders was a nice cold beer this is a fine wine. They really refined it and gave it its own unique, mysterious feel. Currently in the Realm of the Dead. Loving every puzzle. Level design is just as good, if not better, than God of War's. And regarding Zelda comparisons...I don't care if you like Zelda more. There is no denying that is is a better game than f***ing Skyward Sword (a.k.a "Skyward Bore"). No offense to fans of that one...but to me Zelda keeps taking steps backwards these days.
For anyone who thinks my opinion MIGHT be worth a damn...I give it two huge thumbs up! I'd say if this: you like your action RPGs long, creative, brutal, and with lots of quality puzzles and platforming, definitelyconsider buying this. If you liked the first Darksiders, well then you have NO excuse for not buying this.
I give it an 8.5/9 and I'm pretty strict with scoring games. It's excellent. Only thing that keeps it from being a 10 for me is of course the fact that it wears so many of its influences on its sleeve and in such a way that it is often hard to ignore (*cough* Shadow of the Colossus battle *cough*). Like I've stated this is isn't a bad thing since for the most part it outdoes the games it borrows from and its blatant homages don't bother me personally since the whole package and presentation is really satisfying. But it might bother some. Plus the sacred 10/10 score should be reserved for really groundbreaking stuff in my opinion. This breaks no ground. It just shakes it. HARD. Get this f***ing game already. XD