For me, I like that it's the same postures every class and I like the military style. It helps me to stay focused and sort of meditate. I've done other hot yoga classes and felt like I was flailing around and never had the chance to perfect a posture because I wasn't entirely sure what I was supposed to be doing. With Bikram, I know what I'm supposed to be doing and try my hardest to do it. I'm kind of a control freak so knowing what's up next and what's expected of me is really motivating.
This! I'm actually a fan of the routine sequences.
That said, I only did it temporarily because I got an awesome deal on a month pass. After the month was up it was too $$$ for me and the class times/sizes didn't work well with my schedule. I might pick it up again in the future.