I have an exo 5500 and it hauled quite a bit of weight on multiple trips this year. It's well built, comfortable and durable so far.
All that said, I wish I'd have gone kifaru. The reason is that it's far more modular. The exo is very clean but other than waist belt pockets it's essentially two big pockets. That makes it a little tough to organize. You can change bag sizes on both but I think overall if you do lots of different stuff and need 1 system the kifaru might have the edge.
The exo is a good pack, I think some of it really comes down to personal preference.