100% agree with snowbigdeal. I used to be an access rider, and with a open helmet, the avalung worked ok (still a VERY good chance of it getting knocked out of your mouth in a slide imo), but with the types of behaviors we have & gear that we ride with the avalung is much less suited to our sport.
If I was about to cut a chute on a board, I would put the avalung in my mouth just in case, if it didn't slide then I spit it out toward the bottom. If I were to do this same thing on a sled, I'd be sticking it in & out of my mouth about 40-50+ times a day (I mean, just listen to that, do you really want your friends talking about that hose you stick in & out of your mouth...???

) and Like SBD said, it's much harder with a full face, and with it in your mouth, it's extremely limiting.
I kept mine for a couple years after buying a pack, but finally sold it this spring to a skier. Even though it's cheap, I just couldn't recommend one to a friend as I don't feel that when the time comes that you'll need it, that it'll make the difference.
I sold a BCA pack for $450 this year, cheap packs are out there if you look carefully. It's worth the extra money.