I don't know what it's like at other gyms but at the gym(Gold's) I work out at, I would have to say that less than %10 of the people in there don't stretch before a workout. About %25 of those who do don't even stretch properly. I have always thought it is important to warmup first with a 3 minute jog/run/cycle and then get into about 5-10 minutes of stretching before working out.
I noticed on this board that not much is said about stretching/warming up. I am curious what percentage of the serious body builders here do.