I have taken this bag through several countries and about 20,000 miles of travel so far... it has been a great choice! My only complaint is that it tends to tip over with the daypack attached if it is fully loaded, this is easy to avoid by habitually leaning the front of it against a wall if you have to let it go.
The large bag is an ideal size for a checked-bag on the plane, it will accomodate a weeks worth of clothes comfortably and is easy to close when full. The wheels are pretty rugged, being large and well-placed; I am careful with wheeled luggage after several broken pieces through the years but find these to be holding up well. The handle is sturdy and I haven't had any issues with it binding or sticking yet. There are large and comfortable carry handles on the top and side, making it easy to load/unload from vehicles and luggage racks. The shoulder straps hidden in the back panel are functional, though I wouldn't want to use them for more than a few minutes at a time; great if you encounter stairs in a subway station or hotel, but not a hiking pack of any kind.
The carry-on bag is a little on the small side, keeping a laptop and accessories and a DSLR is about all it will take; there is room for wallets, phones, passports and the like in the front compartment. The water bottle holder on the side is a fantastic place to keep an umbrella (I took it to London and was very glad for this). It stores nicely in the overhead bin on the plane.
My favorite coup with this pack so far has been at the left luggage storage in Paris and Dubai, when zipped together you only get charged for storing ONE piece of luggage! This will save you enough that the bag will pay for itself in about a year...
Overall my opinion is that this is the best solution for the frequent air traveler; it is easy to roll on pavement or concrete, you can always put it all on your back for a flight of stairs or unprepared surface, it is well-built and sturdy, it doesn't seem to show dirt easily. I have recommended it to my friends and family.