My friend has the 55, I have the 40, and they're practically identical- literally just slightly taller and slightly wider, at the price of a few ounces. I don't think the backpacker review is invalid because of the difference. Besides, I don't think the Backpacker award is a closer, just a relevant detail. Good call though- I don't agree with them often.
Idk, I just thought I'd give an alternate opinion. The Buttermilk's design team specifically put packs like the REI Flash in their sights and went to the drawing board to get rid of the extras, cut weight, but maintain functionality- that last part is important. For the price point, I haven't seen another pack match up. It carries like an Osprey.
I rip right through open-holed, "cheap" mesh by accident about once per pack. Toss a Leatherman in a pocket and forget about it for 2 miles, and it's gone. I don't like it, I'd rather have the good stuff.
I can only assume your review of the REI's mesh pockets as "probably tougher" is based on clairvoyance! Haha!
When I see a "minimalist" pack that has a sewn-in frame, a lid, and less-than-ideal mesh pockets (when outer pockets are a huge part of minimalist packing) I like to think it's a nice way to trick tourists into spending extra to be like the racers they see on the cover of a magazine. I think there are 5 better ways to spend money, and the Buttermilk is one suggestion from me.
No problem if you disagree :D