Rating: 3 / 5
A couple of disclaimers before you read further:
1. I'm not an ultralight hiker - more of a light hiker (WM bag, MSR Hubba tent, about 13 pounds base weight not including the pack.) As a result, my load is probably a little bulkier than yours.
2. This review is based on a few hours of dayhiking, which is all it took to convince me that I'm going to continue to use my Granite Gear Vapor Trail pack.
This is a nicely made pack. The large number of pockets is great for organizing gear and minimizing stuff sacks. The "swiss-cheese" foam on the shoulder straps and waistbelt is comfortable, at very light loads (not so much at around 30 pounds, which is my full load for a cool-weather week, and what I took for my dayhike.) The Airspeed frame, with it's exaggerated separation from your back, does allow a lot of air circulation.
But: at 3200 cubic inches (in size large), it just barely holds my gear, with no room to spare. The hipbelt starts to "fold" (collapse?) at about 30 pounds, and needs to be pulled almost painfully tight. The narrow "throat" in the middle of the pack (created because the suspension curves dramatically into the pack) makes it difficult pack the lower part of the pack, and difficult to organize gear well. As a result, with my full-out test load, it leaned backwards just enough that I had to fully engage the load lifter tabs - which pulled the top bar of the suspension forward onto the top of my shoulder blades, which got very irritating after about a half hour.
Since it weighs a pound more than my Vapor Trail, is rated for the same weight as the VT, and has a capacity of several hundred cubic inches less than my Vapor Trail, I simply don't find this pack to be a good choice.
I think it might hold an ultralight load quite nicely - but I doubt that someone carrying such a load would want to carry a 3+ pound pack.