The majority of my training is based on 1-2 working sets per exercise, about 3 exercises/bodypart. I typically warm up with a compound lift for my first set, but after that I don't do a warm up for each exercise.
I've actually had harder workouts when doing just 3 sets than when I do 6 sets per bodypart. Dorian Yates always used to point out that no matter who you are, you hold a little back if you are doing multiple sets. When it becomes THE set, you will put a bit more into it. I think he was 100% right. I've had 3 sets of quad training leave me unable to stand. If you are holding back, however, you won't see much from 1 set.