I have been using my Camelbak LOBO for a few years now and it served me well. However, it got caught up on a tree and it ripped an exposed pocket, the lid no longer stays attached to the bladder when open and I noticed that the hose was very foggy and seemed like the inner liner was cracking. It was time to retire the old girl - but I did not want to break the bank.
With a little help, I found the Hydrapak Streamline on sale at BlueSkyCycling.com. A little scared of change, I was reluctant to sway from a pack that I new worked well and last me a while. However, my wallet said give it a go.
Price: Streamline was about 1/2 the price.
Size: about Equal although the streamline "fit smaller."
Bladder: Longevity to be determined, but the measurements on the HP will come in handy if I chose to use something other then water. The CB seems to be thicker.
Easy Of use: The CB's twist cap is another moving part that can break. The HP is fold, slide, done - sure the slide can break off the elastic cord, but that be replaced; unlike the CB plastic connector . The CB needs to be angled to get the water in it, the HP does not require this. Ice would be EASIER in the HP. The CB though stay in the bag and was no fuss. I had to fuss with the HP a little bit to get back in order.
Bit Valves: Cannot answer. I never had issue with my CB Valve and actually kept it just in case I don't like the HP.
Fit: This is a very biased answer, but my CB fits much better. Why? Well I had it for 3 years and thousands of miles. It practically formed itself to my body and the strap are perfect. It will take time to make the new bag into "my bag."
First impressions, I think the Streamline will be a good purchase and I will be happy I made the choice. The price was right ($25). The color, well its sort of lame - but if you can see it, then your behind me

Time will tell, but for the CB addicts, don't be afraid to step out of the box.
Oh yeah, why do they spell it "pak?" I don't get it.