I picked one of the 750ml ones up, and figured I might as well do a short review here.

As some folks have noted, the 750ml's will not fit into a bike bottle cage. Fortunately, the top is a standard size, so you can put it onto one of your regular water bottles. The straw is 7" long, so with my bottle this left 100ml at the bottom that I couldn't drink without removing the top.

Long story short, it's not perfect, but (so far) it's better than either a standard bottle or a hydropack. Hopefully Camelbak will tweak the bottle size a little bit for cyclists at some point.

Compared to a Water Bottle
• Much easier to drink
• Can leave the valve open for quick drinking, without any spills
• Supposedly dishwasher safe, so should be just as easy to clean
• Heavier (not for weight weenies)
• Carrying tab is a little annoying on a bike

Compared to a Hydropack
• No back sweat!!!
• Same valve / draw
• Much easier to clean (so I think you can use it with energy drinks)
• Won't keep liquids cool (and the straw isn't deep enough to use with a Polar bottle)
• You can tell how much liquid you've consumed
• You probably won't drink quite as much as with a regular hydropack

edit: image of the subject in question