I'm a consultant, and I take frequent trips by train to client sites where I spend 4-5 days at a stretch. I did the first few with a conventional rolling carryon and a laptop backpack, but I typically walk a mile or two from the train station to my hotel, and I had trouble getting a full week's stuff in my hardside carryon, so I went looking for something with backpack straps. When I did, the Aeronaut leaped out as the obvious choice.
I have now taken a trip with it, and I'm very happy with it. I swear, the thing is made with TARDIS technology - when I took it out of the box, I was alarmed by how small it seemed, but it holds a lot more than I thought it would. I got a week's stuff in it with no trouble: Four dress shirts, two pair of slacks, four undershirts, four pair underwear, four pair socks, plus toiletries and various gear, and then my MacBook15 on top in a Brain Cell - it just exactly fits. Presto, one bag, throw it on my back for those long walks.
A couple of minor design suggestions: I would've made the main pocket open in the other direction, so that if you pick it up by the handles when you've neglected to zip that pocket, all of your stuff doesn't fall out (yes, I did that). I also would add an O-ring in the open end pocket, so that I could tether things I put in there lest they fall out.
I'm also mildly concerned about the way the backpack straps are joined to the bag. This thing is heavy when loaded, and that seems a possible point of failure. But I'll trust that TB is smarter than I am about this.
All in all, I'm very happy. I wouldn't want to use it in place of my backpacking pack, but I walked two miles each way with it on my back, 25-30 pounds loaded, with no significant discomfort.
One more note: I scoffed at the reviews I read where people complained about the zippers jingling. The noise doesn't trouble me, but it really is surprisingly loud.