No experience w/ Hydrapak, but like the concept a lot. I had a Nalgene bladder that had the detachable hose and it was much easier to deal with than Camelbak, alas, they stopped making them.
A couple reviews mention a plastic taste, I have no tolerance for that but YMMV...
If I were you I'd just get the Hydrapak bladder and keep using your Camelbak pack. Most folks end up having to replace bladders any way and this way you can keep the original as a back up and see if the Hydrapak works as well as claimed, without the expense and fit issues with a whole new pack. Unless you don't like your Camelbak for some reason besides the bladder cleaning issue...
Sit bones = ~135 mm, saddles that work ~ 155cm/6.1 in wide
2003 da Vinci (custom road/all-rounder)/Terry Butterfly Ti
1994 Gary Fisher Nirvana (vintage MTB/commuter)/Terry Butterfly Chromoly
1991 Terry Symmetry (NOS frame/fork, project in progress)
1973 Raleigh Super Course (project in progress)