When I run D&D (or most other games) stats are pretty much considered open- especially in D&D where some of our more "number challenged" players needed oversight as to what their bonuses and scores should be. Since I don't like PvP in my games I don't see the need to keep stats secret. If someone wanted to keep an IC secret, like posing as a different person for example, then that would be fine.
In the Vamp Dark Ages game I'm currently playing in, stats and such are supposed to be secret, but between doing things in game and general table talk that's pretty much gone out the window. We do still have a lot of secret actions, solo time with the GM, that sort of thing. Some of the players take it to silly lengths, like they'll make sure to turn on a stereo if they're stepping into the next room. I think they've been watching too much "Sopranos".
Of course, with the evil plans I've been cooking up for my character recently, I'm sort of glad we have the precedent established...