I run half marathons and have always carried water by hand. No more! The Camelbak hydration pack is fantastic! I've been on a few short and long runs with it and it is great. The weight distribution of the pack is such that I forget that I have the hydration pack on.
I do tend to sweat a little more on my back, but I expected that. Unless someone else can carry the pack for you, I don't see how one would get around the sweating part.
I tried on a different pack from Costco, but there is no comparison. This Camelbak feels and looks phenomenal. The Costco one was bulky, heavy, and looked like dookie.
The amount of water that this holds is huge! I haven't had a problem with not having enough water on a run. Though my longest run so far with the pack has been 10 miles. Not an incredible distance, and it's still raining and a bit cold, so the true test is yet to come. Summer is almost upon us :)
I wore this on a run when I only had a tank top on, and the shoulder straps chafe. So beware. I run with a short sleeve T-shirt now. That got rid of the problem.
The nozzle is fine. I wouldn't say it's easy to suck, but it works. I kinda have to suck really hard (no jokes here please!), but I get the water I need. It could be user-error too; this is my first hydration pack, so I'm not sure if the hose is in the best position. That might have something to do with the minimim sucking power required for a sip of water.
The pockets are very useful. I have my phone, keys, trail map, lip goop, Clif bar, and it all fits nicely. I can reach the side pockets (on the waist strap) while the pack in on my back. I have more trouble reaching the middle pocket though. I have to take the pack off for that; so I end up putting stuff I don't need til the end of my run in there (keys and phone).
I didn't have any issue with the water sloshing. I read another review and the guy suggested filling the reservoir with water, then turning it upsidedown and sucking all the air out of the reservoir. I've been doing that, so I don't know what it'd be like to run and have air in the reservoir. If you're curious, you'll have to find another reviewer to comment on that ;-)
All in all, I am VERY happy with my purchase. It is so much easier to go out on a run and have my hands free, plus have ample room for all my stuff like a cell phone, keys, etc. Purchase this Camelbak Octane XCT. It will not disappoint!
EDIT 19FEB2012: I still love the pack. It's light and really serves my needs for running and biking. I started mtn biking again last fall because my knee was giving me pain when I ran. So, to strengthen my muscles in my knee, I tuned up my bike and hit the trails (and spin class). Well, as soon as I started mtn biking again, so did my husband. He borrowed my hydration pack to aid him on his rides, and at some point when he was learning to use his new clipless pedals, he fell over ON MY PACK! And there it was - a little rip in the pack. I was bummed. I taped the tear... and forgot about it. No problems. But note to everyone reading this: Do not fall with the pack on, or at least fall forward, because the material easily rips on rocks and things. If you do get a tear in your pack, use Gear Aid Tenacious Tape Repair Tape and be on your way.