From reading the DI forums it seems that there are a lot, a LOT of bugs, many game breakers.
Srsly, if you haven't checked it out go and observe the wailing and gnashing of teeth over there.
The handling of the launch was pretty sloppy, day one dlc bonus items not ready, day one patches MIA, the scandal over the "feministwhore" code placeholder, the Steam debacle.
But screw all that, it's still an excellent game, it's hella fun and I guess I've been pretty lucky in avoiding bugs, only one quest was a bit buggy for me and a reset sorted it out.
Kudos to them for concentrating on polishing their product, they know the game is a hit and there are some quite murmurings about GoTY which for smaller players like Techland and Deep Silver is a great boost so it's in their interest to get the game as tight as possible.