Tactical Tailor makes good rucks.
Maxpedition makes durable products (but they always seem smaller in person than they do on their website pictures).
I've found Blackhawk rucks to be uncomfortable (tried five models).
I've found London Bridge Trading rucks to be very NOT-ergonomic.
I've found SpecOps Brand rucks to be less durable than other options.
I've found USGI rucks to be acceptable if inexpensive is a prime consideration.