I've used this thing all over the place, from kicking around Hawaii, to long day hikes, and plenty of mountain biking. Despite being so thin and light, it's held up well through low branch encounters, sketchy descents and being overstuffed for carry-on. The back is way more vented for riding then anything else I've encountered. I'm impressed, I got rid of my camelbaks, and use this as a solution to many problems. As a side note, I use this to carry my DSLR and lenses pretty regularly, and have never had any issues.
If you're looking for a fantastic day pack, I'd highly recommend the Aerios. There's plenty of room inside to hold your gear, and the stretch mesh panels are good for holding everything from water bottles to digital cameras.