i'd recommend AA, not to bash osprey, i have no experience with them, but i had an issue with my AA mid length, the gas block wasn't really straight and the gun was short stroking. emailed them, they asked me to bring it to a gunsmith to make sure my rail was on straight, told them i was at my gunsmith when i emailed them, was emailed back telling me to expect an RMA, the next day i had an RMA. i got the upper back today and it looks like they fixed it. not sure if the short stroking was fixed, but at least it looks straight now.
so i'm pretty satisfied with their customer service for what it's worth. i have an 11.5 inch AA upper that ran flawlessly out of the box as well.