I just bought a Brain Bag to replace my last backpack from Brenthaven. I'd give it a 4/5 based on the following:
+ Great size and flexibility from thick to thin.
+ Seems pretty well finished off.
+ Like the number of pockets for storing stuff.
+ Brain Cell is absolutely brilliant. Best laptop protection out there. Mounting system is fantastic.
+ Freudian Slip is also fantastic. Great idea.
+ Harness is ok, not great, ok.
+ Handle at top is great. Strong enough to hang bag by hook on wheelie, very comfortable to carry.
- Two pockets on front of pack are a shade too small and need more depth.
- Top pocket with hook for keys is too small to easily load iphone, wallet, keys, passport etc.. while going through security checkpoint.
- Disappointing that the mesh pocket does not work well for a water bottle if there is anything of size in the pocket behind it. Most mesh pockets on backpacks have an elastic top and pleats to help make this work.
- Harness needs to have daisy chain and/or D-ring to attach accessories. This is critical if you intend to use it with a DSLR (you're making a camera block, IIRC). Virtually every major strap mfg (upstrap, optech, think tank photo, etc) has a set of tails that clip onto the camera quick release and then expect to attache to either a daisy chain or a D ring. Given that this was a major reason I bought this bag so I could take my camera with me traveling, I'll be having this added at some point.
- Strap ends on umbrella holder (which I will use for holding a travel tripod) need to not be straight finished but finished with ends that prevent them coming undone like the rest of the straps on the pack (harness, waist belt).
- Make the loose ends of the strap captive. Brenhaven does a great job of this. When used with rolling luggage, they tend to drag on the ground and get dirty.
- I'd suggest adding, again now that you are supporting camera blocks, some sort of add on mounting point. I'd suggest MOLLE because there are a ton of accessories compatible with it and when not used, it lies flat and out of the way. I'd put one or two on the outside, and one long one in each compartment.
Good bag. Looks really durable. Should work pretty well, maybe even great once modified.