This is the workout I looked forward to in Xtrain more than any other--I finally did it today (I am following the 90 rotation, but just couldn't wait 4 weeks to finally try it). INCREDIBLE workout! I love tabatas and Hiits in general. For some reason, after doing Insanity, Amy Dixon's Breathless Body workouts, PeakFit/Peak Challenge and even Cathe's Hiit, CF and TTM, I didn't expect this workout to be as tough as it was. I did premix 5--all 5 tabatas and Core #1. By tabata 5 I was ready to be done! I love it when a workout pushes me that hard! Amazing! I've done all of the Xrtrain workouts now except Supercuts (tomorrow!) and I ADORE these workouts! I think they are the best workouts ever!