I love and adore a brutal butt-kicking by Cathe, one that leaves me a sweaty, sucking-for-air blob.
When I got the LIS I thought that would be Afterburn. In fact after doing AB the first time I was sure of it. The 2nd time through, I was surprised at how much easier AB felt, and this week when I did it a 3rd time, I found it to be on the level of IMAX3 in terms of sweatfest, but MUCH more doable than the 1st time through.
I came away realizing that for all-out all out, there is nothing IMO, like Intensity. I love love LOVE that workout. That wind-sucking, chest-exploding, cry-for-mercy is the best, and Intensity delivers like no other (well, except for maybe an A-Jock mish-mosh.) Give it a shot and enjoy.