So to give a sense of what the compartments can hold have a look at these:
|The Main Compartment|
On the days I am packing this to the office, the main space holds a 27 oz Kleenkanteen bottle, and ice pack and a plastic food container or two. I the lid, I typically have a pack of gum zipped up. This is a bit tighter but still not a strain.
If you do some reading you will find that the front compartment can be configured as a top and bottom half each with separate zipper access or as on big compartment. I run top and bottom all the time. I keep batteries and a petzel light in the bottom.
As far as carry goes, it really is an ugly thing to look at. In terms of function though, this one is really well done. The wide strap and shoulder padding make it comfortable to carry and the ambi design let's you shift sides without issue if it gets heavy or whatever. It's a really nice design. If the looks and size are what you are after, I have to say I think it's worth a look. I'll hang on to mine for a good while.