I disagree with Daveinjax on this one....I've had 9 different Kifaru packs in the past, and the Kelty Cache Hauler smokes them all on heavy loads in my experience and testing.
I've done a lot of heavy load testing over the last spring and winter, and the Kelty CH is one of the two the most comfortable I've used.
The Kelty is very comfortable at heavy loads, but it does have weaknesses. With any external frame pack your shoulder movement will be limited, and it will seem a bit rigid and clunky. Also, it'll be noisy if you're busting brush. And you have to realize that you can get one of these on sale for $95, so the fit and finish are what they are....you will probably need to plan on scrapping the stock wings and the load shelf. Rope or a ratchet strap will hold up a lot better for securing a big load in my experience.