For those unfamiliar with the original Pit DVD workout, they are lead by John Hackleman, trainer of UFC great Chuck Liddell and highly touted MMAist and grappler, Glover Texiera. Hackleman is an expert in Hawaiian Kempo. The basic principles of the Pit workout is to exhaust the body with rounds of body weight exercises, such as pushups and squats, and then further train your exhausted muscles and anaerobic capacity by punching and kicking a heavy bag.
I didn't like the original Pit workout very much for a few reasons. Firstly, the workouts were too long. At about 70 minutes, not only were they inconvenient, but grueling past the point of quick recovery. Also, there was a lot of wasted time/ overly repetitive movements which made the workouts boring (3 straight minutes of squats into front kicks followed by three straight minutes of squats into sidekicks, for example). Lastly, the original Pit DVD was divided into an upper body day, a lower body day, and a complete body day. This is a concept borrowed from body building where muscles are intentionally isolated. It was odd when applied to a martial arts where movements are not designed to be isolated.
The CrossPit DVD addresses many of these concerns. Although these workouts don't resemble the actual Crossfit program too much to my mind, Hackleman used some of their training philosophies to give his Pit workouts a much better structure, which was the biggest weakness of the original DVD. The CrossPit DVD is divided into two workouts. The fist focuses on the Tabata structure of 20 seconds of all out work followed by 10 seconds rest. (This format has become very popular in "cutting edge" workouts in the last few years... athough calling it "Tabata" is somewhat of a misnomer, because the actual Tabata protocol is much more specific that just a 20/10 breakdown of work and rest. Google "Tabata Protocol is you are curious where this concept comes from).
The second CrossPit workout follows the Chelsea pattern, where you have a given amount of time, either 30 seconds or 60 seconds, to complete a certain amount of work. It is up to you to pace yourself most effectively (ie. Do you want to get the work done in an all out sprint and then have a good chunk of time to rest, or do you want to adopt a slow and steady approach?)
Both of the CrossPit workouts are full body workouts that incorporate pushups, squats, squat thrusts, pull ups, ab work, punching and kicking; Hackleman abandons the goofy upper body/ lower body split. Also, both of these intense anaerobic workouts can be completed in about 35-40 minutes, a much more reasonable amount of time than the original Pit workouts required. Overall these workouts are much better paced and a lot more fun. They are challenging, and you'll be dripping with sweat, but you won't be so ruined that you just want to sit on the couch the next day (Google: Symptoms of over training :) You might even have the energy to do some of the Crossfit WOD's (workout of the day) on the off days. See crossfit.com for the WOD's.