I did day 1 of level 2 last night and thought I might vom a couple times... I drank a spark before I did it and that probably wasnt' the best idea... I normally drink it before I run and I love the added energy, but there are tons of plank position moves and being in that position repeatedly with that much fluid in your stomach was horrible!
The level 2 workout is definitely a lot tougher than level 1, I can't imagine what level 3 is going to be like. Eeeeek!!! I made it through it though with only a few 5 second rests. I'm really looking forward to and hoping that it gets a lot easier after a few days like the first level did.