I have been trying to do this style of training for a bit. I just notice that my "energy" levels are always up and down. I've got a alot going on in life lately: getting married, moviing, exams, work, etc...
This style of life makes the 3 on, 1 off, spread I envisioned pretty difficult to recover from. I guess I need to really figure out what is more important: sleep or training - many days I have to make that decision.
But I do like not being too mauch of a slave to a particular protocol.