yep used it alot over the years - quality is pretty much the same wouldn't be shocked if they are made in the same factory
one draw back with the Flyye is it doesn't come with the bladder - but then the Casmelbak one is pretty poor - getting a
Source one would be a better investment.
Did spot these guys doing the camelbak alot cheaper than I've seen elsewhere though so the price difference is neglitable
http://www.tactical-kit.co.uk/camelbak-hawg-30-litre-hydration-system-1050-p.asp
you do get more colour options with Flyye ( camelbak dont come in Coyote Brown, Khaki, Ranger green or OD)
I also believe its 1000D rather than 500D which seems to be the new Camelbak material - The CB will be lighter and material thinner but most military gear is going towards 500D these days as the wear resistance seems to be decent and they like the weight saving...