I stopped by Runner's warehouse on the way home from work and picked up the Camelbak Octane 8. I tried on the Nathan 2.0L and it was really neat, but I could not even carry a rain jacket in it.
I'm not there yet, but a four hour run in the desert would be great some day... What kind of strap did you use for your hand held bottles? Runners warehouse had some for between $16 and $25 with straps. I'm not sure about the straps...