I've been doing this workout for awhile and it kicks major ass. I get in and out of the gym in less than an hour. Most of the workouts I do in my garage with a pull up bar and some dumbells. There are marines, SEALs, cops and firefighters that do this for their regular routine. It is gauranteed to get you in the best shape of your life, and the best part is it is free!
However, these workouts are very intense, so don't feel discouraged if you have to do scaled down versions of the workouts until you get stronger. I had to start at half the weight or half the reps for awhile. I'm still not quite up to 100% intensity, but I've only been doing it for about a month. Just to get you an idea of how well it works, I never did pullups very often. I weigh about 185 lbs and I could do maybe 2 pullups with good form when I started this workout. Now after 3 1/2 weeks, I am doing 14 pullups with perfect form. I don't kick my legs or go halfway down or swing. I go all the way down until my elbows lock and all the way back up in a controlled motion. I know 14 doesn't sound like much, but everyone thinks they can do pullups until they try. Also, I can easily do 100 pushups without stopping, I can do nearly 200 situps. I'm also running 5 miles at a time with ease. The best part is that I have my 6 pack back, and then some.
So check it out, its pretty awesome.
http://www.crossfit.com