Hot yoga actually allowed me to forgo all traditional cardio in my recent contest prep. I've never been a big cardio fan for achieving favorable body composition, so the ability to eliminate it completely was very attractive to me. Here's a photo from prejudging. (That's me in the center.)
I believe hot yoga has significantly contributed to my health, mobility, recovery, insulin sensitivity and body composition. It's not a daily practice for me, but I do participate in at least three sessions per week of hot Hatha.
I honed in on hot Hatha for a number of reasons. First, the room is hot. It's 100 degrees if I place my mat underneath the infrared overhead space heaters. I own a dry sauna at home which runs at about 140 degrees, but 60 minutes in a hot Hatha class provides the same benefits including detoxification through excessive sweating, recovery via increased blood flow, and activation of heat shock protein to protect against insulin resistance.
It also focuses more on balance and stretching. This is a good thing because it doesn't cut into my training capacity or ability to go balls-out in the gym, provided I stay well hydrated. I have a serving of Mag-10® throughout the hour-long session to ensure I don't cannibalize muscle.