I get NFL Redzone, so I get to see parts of all the games, and all QB's do it. Maybe not as often, but they all do it. It's part of reading the defense, trying to get them to show their hand, and making adjustments. What has hurt the Cowboys over the years, is not having a center that was good in shotgun, whether it be working in sync with Romo, or making good snaps.
As for the defense, anybody on the DL better not be looking up at the playclock. They're watching the ball. I suppose a LB could look at the clock and try to judge when to start, but he typically moves early, and shows his hand. It's not like Arena League, when you see someone coming in full speed toward the LOS (yeah, I know that's offense, but you get my point). I want those guys to jump early, so I can see who's coming from where.
As raw as our OL is, they need all the time they can to try to read what the defense is doing. Unfortunately we're just not at the point personell-wise, that we can just say "we're gonna run what we want to run, when we want to run it," regardless of what the defense is doing.