Are you asking how many rooms we decorate, or how many of them are finished?
If it's the latter...none, yet.

We normally decorate this weekend, but due to work and family stuff, we didn't have time. We'll get it up next week, though.
As for how many rooms we decorate - well, pretty much all of them! I guess the only rooms not decorated are the master bath, and the office. The girls each have a table top tree and Nativity set in their rooms, and I put Christmas towels and bath mats in the girls' bathroom (which is also the guest bathroom, so it has to look nice - lol). I even decorate the kitchen! I *love* Christmas. We have 12 big totes of decorations and 3 full-sized trees. Fortunately there's lots of storage in the attic.
Your post reminded me of something, though. When I was little, my Mom used to have a toilet seat cover with Santa on it. When you lifted the lid, there was Santa again, with his hands over his eyes.

We always got a kick out of it.