It's weird that the Hitman series, a game about an assassin is one of the few series out there that bucks the trend of combat above all else and is the closest we've had to a pure popular mainstream adventure game for a while. The great thing is that you can play it as shoot anything that moves and enjoy it on that level or you can revel in the puzzle aspects. Also, coming back to the quick-save issue that's been discussed, Blood Money introduced infinite quick saves on the easiest settings and I really appreciated that as it allowed you to experiment at will and try outlandish things, even if your only reward was a comedy death, you might otherwise have skipped for fear of losing half an hours play.
I'm hoping for some elements like that in Bioshock, I'm sure they've talked up being able to set off various groups in Rapture against each other in previews before now.