All great points in this thread. Been going for 5 years now. It's not for everyone for a number of reasons. It's worked for me mainly because of the time factor (I work nights so mornings and early afternoons are flexible) and because the workout is sustainable for me. I'm a former college FB player with a history of multiple surgeries on both knees. Major impact like running and jumping causes swelling for days. I've been able to modify the workout slightly to alleviate those issues and haven't gotten hurt while there.
I started out at 6-3, 290 lbs with body fat over 30%. Got down to below 200 which was not sustainable for me, but it was my initial goal. Been right around 230 over the past 4 years with 17% body fat. The nutrition program is a good guideline, I took it a step further and met with a nutritionist who simplified things for me. My weight history used to be like a previous poster, get in shape, lose weight, then pack it on again. Now, I still have swings, but they are only 5-10 lb differences as opposed to 30-40 lbs.
It can be a little cult-ty as someone stated, but so can working at any large company. Avoiding idiots is a lifestyle change as much as a fitness and nutrition routine.
As for supplemental workouts, I try to make my Farrell's workout one of two workouts in the day. I ride my bike when I can, but the latest crap weather has had me either running on the treadmill for 20 minutes (it's all my knees can handle without swelling) or a supplemental weight workout with dumbells.
Hope this was helpful.