Kettle Bell workouts?...thoughts?

I have been looking into getting a few kettle bells. I was wondering if anyone does or has trained with them?
I love the compound movements and the cardio aspect that you get with them....

I personally haven't used them, but have seen people working out with them in the gym. Looks cool, it seems like alot of the personal trainers at our gym like their clients to use them.

Ive thought about picking some up myself. I subscribe to Budovideosdotcom on youtube for "Glover's Travels" (very cool little show) and they have a very cool kettle bell series.

YouTube - Kettlebell basics with Rik Brown - Warm Ups

I have never used them but they look like something great to incorporate into your training!!! I have seen tons of mma dudes and the guys who train for the world's strongest man competition use them in their training!!!!