Just in case!
You should never get safety gear to justify taking bad descisions or going places you shouldn't. Period!
That said, I got the Avalung because I was already going off piste skiing and even if you minimize the risk, it's always there.
The avalung fits perfectly over the jacket and I use a Dakine Heli Pro backpack and it doesn't interfer with the Avalung. While riding, I was never concious about wearing it, which is a pluss. It's like the avi reciever, I never think about wearing it.
Negative: It's hard getting it out of the protection neoprene and if you have the mouthpiece out and crash, it easily get's filled with snow.
I'm glad I got it and hope I never have to use it. (I got two, one for me and one for my girlfriend. Hope she never has to use hers either).