I took this as my only bag on a ten-day trip that included three flights, two trains, several metro rides, and a few miles worth of walking to and from hotels. This bag did very well. To keep the bag from bulging, I used a set of eBags Ultralight Packing Cubes (worth the price--I tried some other cubes). The set is just the right size with my rain coat folded in between and a hoodie stuffed into the top.

I think the cubes helped a lot to keep the bag in its natural shape so the zippers never seemed stressed. The way I packed it, it also stood up on it's own. Here is the list of the gray and blue things I packed (as shown in the pictures) for a spring-weather trip to provide some idea of the capacity: rain coat, hoodie, pair of shoes, 4 t-shirts, 2 collared shirts, 2 pairs of jeans, swim trunks, a variety of socks, underwear, and a small cube (6"x6") with chargers, plug converter, meds, and toiletries. (and the packing cubes of course)

In the outer pockets I had a folder with all of my printed stuff, bag with sunscreen and liquids for TSA screening, earbuds, two paperback books, and sunglasses (next to the books).

I would definitely recommend this style of travel over a suitcase. No waiting for baggage, no stress with stairs or curbs or puddles or metro "gaps", hands are free to deal with metro cards or passports or whatever, and there are no wheels so you can carry it on your lap when you sit.

My one criticism is that the cinch-straps are attached to the outer pocket, which I guess helps pull it flat too, but I'd rather it was just attached to the main enclosure's outer panel.
(8 photos of the bag as-packed are attached.)

Purchased this for an upcoming weeklong trip to San Francisco and while I have not used it yet I did pack it with everything I anticipate to bring with me and I'm surprised it held it all! I typically travel with a wheeled carryon and a crossbody as my personal item but I wanted a backpack so I wouldn't have bulky luggage in the BART. I took a picture of the backpack fully packed next to my usual carry on. I tried to draw over it to highlight the size difference, the backpack is slightly more compact than my luggage and holds the same amount of items. I didn't do anything special with the packing, no packing cubes or compression packs or anything. I only used the inner straps to hold everything in place and tightened them to squish the clothes a bit. My only squabble about those straps is that one of them was put in the wrong way, so it'll have a ripple when it's turned the right way so I can snap it in place. But it's not a deal breaker and it's not worth sending back either when it still works.

I packed 2 pairs of jeans, 4 skirts, 2 pairs of leggings, 7 shirts, 1 long-line cardigan, underwear/bras, and a travel bag of liquids/toiletries. The only items I didn't pack would be personal items (like wallet, snacks, etc) and electronics (kindle, chargers, powerbanks, etc) that I typically carry in my purse as the under seat item anyway. Overall pretty happy with this backpack! It will hold a lot more than you think.

Good quality, I'm sure this will last me a few years. I was mostly concerned with the size when I bought it, since I was going on my first 'basic economy' flight on United. Packed 3 days worth of clothes and it fit sort of okay under the seat in front of me (a little bit too long, see attached pic). The straps inside were nice as it kept my clothes from getting thrown everywhere. It was easy enough to get the back straps tucked out of the way before boarding the plane.

The attached pic is on United's basic economy seat.

I bought this backpack for a 2-week trip through France. The size is great, it felt comfortable on my back, and it looks stylish. However, the zipper slider completely broke on day 4 of my trip. I had read reviews and saw that other people had the same problem, so I was extra cautious to not over-fill the bag. It still broke.
I contacted the company after I returned, and after several emails they offered me a partial refund of $11. I agreed to the refund because that would be enough to have the zipper replaced. Once I agreed, the company emailed me and stated that they would be giving me a refund of $5.50. This is not enough to have a tailor replace the zipper.
I like the bag, and I am going to pay to have the zipper replaced, but in hindsight I would just purchase a higher quality bag. The materials used are not adequate to do any serious traveling with this luggage.

I searched high and low for a carry-on item that would hold the maximum amount of volume and still count as a personal item. This worked great for American Airlines as my 'personal item'. The height dimension is too tall for a personal item, but I left about two inches of space to make it fit into the correct dimensions. It fit nicely under the seat of an Airbus 330-300. If stuffed to the top, this would classify as regular carry-on item, still fitting in the overhead bin.

The interior does not have a ton of pockets, but considering how much you can fit in here, it doesn't really matter. You may want to get packing cubes or buy the option that comes with packing cubes (I use some Ikea ones I bought a while back). This will help keep you organized.

Other cool features are the pockets that allow you to hide the backpack straps, so you can carry like a normal piece of luggage. I tested the stitching before I packed and everything was solid.

I searched high and low to find this and it works great for what I needed.