I too have decided to jump on the bandwagon and give it a try. I have found that the "sevens" at the end of the workout really give quite a burn and train the glycolitic elements of the muscle quite hard.
I do think this might make new demands that my muscles aren't used to and are almost certainly the drivers for why so many people seem to like the system. Most likely, it also helps with adding capillary density and thus improves long term gains because recuperation probably improves.
Keep us updated on your progress!