Without having had one, I always felt the A30 would be too small and the A45 too big, if only because I had plenty of 30L Travel bags.
Queue this Christmas, where I wanted to buy my dad a serious travel bag for business: I actually sent him links to the Western Flyer and Tristar. On his own, he requested an A30.
My girlfriend and I went to the factory to pick it up and she instantly honed-in to an aubergine A30 they had in the showroom. Well that became HER Christmas present then. She got me a Brain Bag in the same color too (see the other thread for my BB review if you're curious about this VERY impressive bags. I mean the word 'impressive' very much here).
I had to take an impromptu 2.5 weeks trip to Europe, in the heart of winter. I really wanted to take only the BB, but it proved impossible. I'm either not good enough a 1-bagging yet, or it's much tougher to do in winter (I suspect both). My infinitely-better half kept insisting I took her A30 instead. I finally gave in (with a Topo Design Commuter briefcase for my laptop + flight accessories).
I am LOVING it.
First it's important to specify this is NOT a tech bag. It is NOT meant to fit pretty much anything at all that is not clothing. You can try. You may even somehow succeed. But it's not what it's meant for. It's also not a replacement daypack. If you travel with the A30 and it only, it's likely you may find yourself missing another bag to just carry around. For me this is a business trip, so I'm fine with it + briefcase.
As for it is: it IS a duffel, not a backpack (more on this later) in the way it is designed and the way it packs.
In this role the A30 is fantastic. It fit everything I gave it with some small headroom left, it carries comfortably with the shoulder strap (I had it for 5 hours in Schipol; it's obviously not a hiking pack or lightly-filled S25, but it carries as if the shoulder straps were definitely designed as more than a mere afterthought).
As always the #10 zippers feel fantastic; the bag is very-well built and feels just solid. It's a little stiff for now, but it will loosen a little over time (the curved zippers in particular are a little hard to open at first).
For me personally the only two issues I have are:
* While I can open-up the side compartments to increase capacity on the middle-compartment, in practice it's not all that useful as the expansion is limited
* I do not need, understand, nor am able to use the thin end-pockets. The zippers and extra fabric add weight which I can't find a single use-case for
And I guess that's it. For reference here was my packing list:
* 1 jean
* 1 Kuhl travel pants
* 2 shirts
* 7 t-shirts
* 2 wool t-shirts
* 7 pairs of socks
* 7 boxers
* Rainjacket (Arc'teryx Interstate)
+ Electric toothbrush in its case (which is also its charger), travel toothpaste, floss etc... I travel without toilettries: I can easily find this in airports at my destination if I need, and in this case I am at a hotel anyway..
I'd say the bag was 90% full. with more careful packing I could have fit perhaps a couple more clothing items. No shoes, extra jackets or similar though. On me I had my Patagonia Down Sweater, hat, scarf and gloves which ended-up in the briefcase for the flight.
So it turned-out I never needed an A36, because there's a big difference between what a 30L backpack can take and what a 30L duffel can take. I regret not being able to travel solely with my BB, but I also recognize it may have been more of a hassle, especially in airplanes where it wouldn't have fit under the seat and I would have had to take many small items out.