it requires you to decamber the ski which depending on the size of the ski could be alot of up and down movements. up and down movement are for more effort beside the fact that in the EC you simply dont have the time to 'purpoise" all the time.
as I stated above it takes more speed to get more float for a similar ski meaning that a cambered ski is going to have be going faster to turn. Faster to turn is actually 2 fold here as the rockered ski can pivot and turn with almost not speed but the camber ski would need enough speed just to be decambered and then enough speed to keep the ski decambered though out the turn.
Lastly the camber is creating pressure points in the front and rear of the ski instead of the entire ski itself. Skiing it in powder is again fighting its general design.
there certainly is no advantage to camber in powder from a pure performance stand point. there is an advantage to using it on hardpack though as its already been stated. For true All mountain skiers back east(ie someone who avoids groomers like plague) camber has little use as even in hard pack trees and bumps the likes of the 100mmish hybrid shapes are much quicker and easier to handle than any cambered fat or mid fat.
lastly Jaobrien Id do agree "the one" would be a much better DD than a Obseth.