I have the 2010 model of the CamelBak classic and I love it! I mainly use the Camelbak for mountain biking, and I have to say that it does an awesome job.
I really like this thing because it holds a lot of water and it does a great job of distributing it properly throughout the bladder, which allows for it to have a low profile and stay close to my back when I ride. I also like that if I put ice in the bladder before I ride, it keeps it cold for almost the whole time!
Lastly, I think that it is awesome that the bladder is removable because I can take it out and use it in both my REI flash 18 day pack and my Osprey Kestrel 38 pack. I cannot say enough good things about this thing. If you are on the fence about buying it, then I recommend that you pick one up!