I ordered my Aeronaut in September and took it on a 5-day trip to Maine with my girlfriend. She liked so much that I ordered one for her a couple weeks later, and we have since made 2 more trips with the bags -- a 4-day trip to Colorado and a week-long visit to North Carolina. I also took mine on a 2-day business trip to western Minnesota. We've gone carry-on only on each trip, and so far it's worked out great. I usually take the Aeronaut and an Imago -- she takes her Aeronaut and another small bag. I typically take my laptop along, and with that and the 3-1-1 toiletries bag, going through security can be a little hectic. Still, it's worth a couple minutes of fumbling through security not to have to worry about late/missing/damaged baggage later on. And the one-bag method definitely forces you to prioritize and not over-pack.
Here are a couple headless shots of us on our way to Boulder in October....
...and on our way out the door to North Carolina in December.
For reference, I'm close to 6'0" and my girlfriend is 5'2". The Aeronaut is pretty big on her, but unless it's loaded to the max (as it was on our way to NC), she's been able to carry it comfortably in backpack mode or with the Absolute shoulder strap. I prefer to use it as a backpack when in the airport or when trying to go quickly from one place to another (to/from public transportation, etc.). Otherwise, the Absolute shoulder strap or the grab handle both work well.
As for what it will hold, on our trip to NC I took:
2 pairs of jeans
3 long sleeve t-shirts
4 short sleeve t-shirts
1 long sleeve button-down shirt
1 pair of sweatpants
4 pairs of boxers
3 pairs of socks
mp3 player in box (gift)
One end compartment:
1 pair of size 11 running shoes
2 pairs of socks
Other end compartment:
3-1-1 toiletry bag
organizer pouch with other toiletries
pouch with electronics accessories (mouse, ipod cable, phone charger, etc.)
Before finding Tom Bihn I had previously used an LL Bean duffel bag that was too big to check, a flimsy shoulder bag, or a carry-on rolling suitcase that didn't seem to hold much besides a pair of shoes and one change of clothes. Not a good option among them. The Aeronaut has been a wonderful change, and for my purposes -- leisure and casual business travel -- it's pretty close to a perfect bag.