1st gen ULA Conduit, it just works and is so comfortable. My only change would be to have GG-style mesh pocket for a SitLight pad. That said, a GG Gorilla may be in my future.
What ULA packs do that allow them to carry so well (and what I've yet to see from any other manufacturer) is where the shoulder straps attach to the bottom of the pack. Not the bottom-front where the hip belt attaches, but the bottom-back where the big outer mesh pocket stops.
Actually, I just checked and the newer models don't do that anymore, bummer.