It has space for 2 SLRs, and around 5-6 lenses OR a compact medium format system, along with space for a large notepad computer (most 15.4" screen laptops fit, my 15" unibody macbook pro fits perfectly) and lots of room for accessories. There's loads of room in the front pocket for my lunch and some pens, paperwork, keys, phone, purse, whatever, and there's a pouch that unfolds at the front along with some bungee cord to hold a tripod snuggly in place. I found a clip inside the front pouch and after wondering what it was for, I figured it'd be perfect for keeping things I often lose in the depth of my bags in place for easy finding later, like keys, my phone and possibly my purse. There's lots of other little pockets to put things in and the ones inside the camera section are laminated mesh, so they'll be weather proof.
The sections inside the camera compartment are fully adjustable as they attach very securely with velcro. So securely in fact, it's sometimes hard to un-attach them! On the outside at the bottom of the bag there's a compartment held closed with velcro which contains the all-weathers proof cover which stretches over the bag and can be tightened with a bungee cord. This will probably also double as an anti-theft cover as thieves would have a hard time getting into the front-most compartments without my knowing about it. All of the zippered compartments are secured even further from the outside with lips that cover the zipper and a clip that fastens over the zipper to prevent it from opening. The bag also has adjustable straps on the front attached to the bag and very padded shoulder straps which go over the sternum and across the abdomen, further aiding the comfort of wearing the bag. It has lumbar support and a padded mesh back, and a carry handle at the top. All sections inside are very padded, and I have no fears about carrying my laptop around inside of it. It's probably safer in there than in my other laptop bags!
As you can see, I'm very very happy with it, and it has more than enough room to keep all my future lenses and bits and bobs, including my laptop, lunch, and whatever else I decide to take with me like chargers and batteries. This is great because it now means I won't have to use my college rucksack anymore (which is literally falling apart at the seams) and I'll be able to take even more around with me in complete comfort, including my lunch :)

