This bag is absolutely brilliant. I travel carry-on only, packing a smaller "day bag" inside for daily essentials; water bottle, umbrella, meds, etc. once I arrive at my destination. My ultimate goal was to eventually travel only with that day bag, but at around 12 liters, fitting a week's worth of clothes is virtually impossible.
I bought the Aer Go Pack 2, which at 43x28x14 cm seemed like exactly what I was looking for. (Although I usually avoid Aer or Alpaka because of the shiny TPU-coated zips—they just look bad in my opinion—but luckily the Go Pack doesn't have them.) It's a great bag and easily fits a week of clothes, but once you empty it out to use as a day bag, it turns into a floppy mess. Bags like the Osprey Daylite or Transporter 26+6 are also great for the flight, but they aren't what I'd consider ideal day bags either.
For me, this is where this bag stands out as an absolute winner. It’s spacious enough for a week's worth of clothes (assuming no extra shoes, wearing your jacket on the plane, or alternatively just add a "drip kit" to be able to store the jacket, or whetever else on the exterior). Most importantly, because it has built-in structure, it maintains a clean, slim profile when nearly empty as a day bag. Add in the ability to roll back the interior mesh divider to turn it into a regular top-access pack, and this is hands down the best true "one-bag" travel solution I’ve found, and I’ve owned a lot of bags, like 30+ a lot).
A major shout-out as well to whoever at Matador managed to create a weatherproof MATTE-finished zipper that actually looks great! I'd also recommend adding a Speed Stash for a bit of extra storage and quick-access for a passport and phone at the airport.
Definitely picking up the packable duffel next and keeping in the laptop compartment for whenever I know that I'l need extra space to bring things back home.