Active noise cancelling headphones?

Anyone here use them?
I've seen dj's using closed back cans and IEMs, but never active NC phones..

I personally use the bose qc15 since they're so light and comfy, and they're amongst the best cans i've tried for one-ear listening, since the headband bends nicely around the ear and it doesn't slip off at all.
The only problem i've had is that when the battery goes low, the headphones start turning off when they try to compensate for something very loud (say, a kick drum during a set), so i always carry some spare batteries with me.

Other than that they really isolate you from the outside world, they're phenomenal for mixing in songs that start out with a low volume :)