I picked this game up at the latest Steam sale and beat it over the weekend.
I enjoyed it immensely. It's probably the best RE game since RE: Zero (not counting RE:ORC which is great, but an entirely different style of game).
I've read a lot of comments about how it's more like the classic RE games, and that's sort of true, but don't go in expecting another RE: Make. There's definitely a lot more emphasis on atmosphere and exploration than, say, in RE5, but there are still some traits from the newer games like a lot of running & gunning, rail-shooter sequences, and many action-oriented set pieces. Luckily, the barrage of QTEs that plagued RE6 are much reduced here.
One thing that I think RE:Revelations proves is that you don't need fixed camera angles and crappy controls to make an atmospheric survival horror game. The narrow, branching corridors and obstacle-filled rooms mean that you often can't see very far ahead of you and have to rely on sound to know if there is an enemy lurking nearby (just like in the classic RE titles).
Another thing I really liked is the weapon upgrade system. Basically, you find various weapons parts that allow you to change aspects of your guns. The parts aren't locked in once you add them to a weapon, so you can take them off and add them to a different weapon later. A lot of the parts lets you do basic things like increase damage, reduce reload time, or hold more ammo in a clip. But then there are some more exotic parts that do things like let a gun fire two shots at once or do increased damage as enemies get close. It reminded me a lot of the weapons customization system in the KOTOR games.
The campaign took me about eight hours to beat, and there's a whole Raid Mode that I haven't really delved into yet. I would definitely recommend it to fans of the early RE games.