Nearly perfect. It's unusual I give a review of this level of detail.First, let me say that if you're debating about getting this bag - get it. 100%.Second, I bought this bag for a recent two week trip to China. The trip involved quite a bit of moving around the country and there weren't too many consecutive nights in the same location. I also had to take a couple trains and domestic flights in addition to my multileg flights back and forth. That said I was looking for something that could hold a lot of stuff, be easy to grab and go, and also work nicely on an airplane without having to check it. And this bag fit the bill incredibly.This bag is amazing! It's almost a perfect carry on bag AND almost a perfect backpack.How I used it:I carried this bag along with a regular sized backpack for my two week trip. When I was traveling from place to place via train, plane, or bus... this is what carried the bulk of my belongings. During the days when I was sightseeing or hiking, I pulled out my clothes and such and used it as a day pack to carry my water bottle, camera, lenses, first aid, toilet paper (China), etc. as it was more comfortable on my back than my regular backpack. During my flights, I used this bag as a carry on every time and it always fit wonderfully in the overhead compartment.What I love about this bag:1. The backpack straps and great. With Osprey being a backpack company first, I'm not surprised that these are good, but they really are great. I walked nearly 100 miles in the two weeks I was in China and this bag was almost always on my back. It is comfortable when it's heavy, when it's light, and for long periods of time and distance. The chest strap is always nice but the best parts are the top adjustments and the waist strap. They could have easily been far too undersized for the capacity of the bag but I was really impressed at how comfortable this bag is to wear. (p.s. I'm athletic build, 5'10'', ~32'' waist, and ~170lbs).1.5 The fact the straps hide away in their own dedicated compartment is awesome. This made it super easy to manage the bag when getting on/off planes and in/out of taxis without having to worry about straps flying everywhere and getting caught on stuff. Also, even when this pack was filled to capacity, the straps were still easy to put away and take out.2. The straight jacket buckles. These serve two purposes. The first is more obvious in that when you pack the bag full, or even not full... it compresses it down smaller and removes any bulges or slack in the fabric. I also like how it takes some of the stress off the zippers when it's extra full (although the zippers seem super solid and I have no reservations about them). But the second feature is that it's a layer of security. When I was carrying this pack around as a day pack, I had very little worries about anyone being able to stand behind me and go through my back without me knowing because of the extra steps it would take to get it open. I found this to be hugely reassuring and comforting which let me focus on the mountains and cities rather than worry about the stuff on my back. Bonus: they also are super handy for holding a jacket to the pack when it starts to get warm out and you have to lose a layer.3. The "laptop" sleeve is great for more than just laptops. It also has a zippered mesh pocket inside which is perfect for keeping extra cash or such when traveling as it'd be impossible to get into while the bag is being worn. Furthermore, the laptop sleeve itself was perfect for storing my light weight rain jacket should I get caught in the rain and need to access it quickly without having to take everything out, or even open, the bag. I also see how it would be super convenient for using as a laptop sleeve when having to go through security at airports as well.4. The padding. This is not a flimsy bag. The sides are well padded as well as both sides of the laptop sleeve. This it PERFECT for someone who carries a bunch of camera gear and likes to keep it protected from bumps and such during travel.5. The top compartment somehow is magically still useful even when the bag is packed full. This is a perfect place for sunglasses, chapstick, hand sanitizer, or other things that may be frequently needed or easy accessibility is preferred.Alright... but how much can it hold?For my trip, I packed it with the intention of not doing laundry.Which included (more or less):16 athletic type t-shirts1 long sleeved shirt19 pairs of underwear16 pairs of socks3 pairs of pants2 pairs of shorts1 pair of sweat pants1 rain jacket1 down jacket1 bathing suit2 knee bracespersonal items (tooth brush/paste, deodorant, etc)misc stuff like ear bud headphones for the plane, passport case, sunglasses in a case, etcSo why only 4 stars?1. I really would have liked to have some kind of external water bottle holder when I was using it as a day pack. I understand that it doesn't really fit into the concept of this bag, but the guys at Osprey I think are creative enough that they could have come up with something slick. Not really a deal breaker though.2. The side handle is too far to the back side of the bag to be comfortable. When using it, it tends to carry the bag at an awkward angle that causes it to hit/rub/interfere with your leg as you're walking (see picture). Simply moving it so it's more centered in the side of the bag would have fixed this. Not a huge deal but made it less useful in the bag form over the backpack form.3. This is the main reason why I deducted a star... Just include the shoulder strap! I wasn't surprised that it wasn't included after the purchase because I saw that it is sold separately before I bought it, but come on. The clips look great but whatever the cost of the shoulder strap could be doesn't justify it not being included. Even if the cost of the bag was $10-20 more and included the strap out of convenience that would have been great. I just feel like having to source and purchase the strap accessory separately is ridiculous.