I use a Kelty Cache Hauler... with the load wings, not the full bag. It's no Frontier Gear, but it's as comfortable as can be expected with 100+ lbs, and was about 90 bucks. The wings are nice for securing a "squishy" load.
You couldn't pay me to carry another load on a Bull Pac...
I was going to ask if anyone had used the Kelty. I have been thinking about upgrading from the old military surplus ones we've been using. Those straps are killers on the shoulders.