A little late...but oh well.
I've owned the Exos 34, Talon 44/33 and the Hornet 32. I just picked up the new arc blast with the horizontal suspension beam and the fully taped seams in the blue color. My first cuben fiber pack.
I always thought my Ospreys were great, comfortable packs, until I tried the Arc Blast.
The arc blast is basically waterproof, the volume can be greatly controlled with the roll top, the netted back panel feels like heaven, the straps are a lot wider and the suspension system feels a TON more stable....even compared to the exos. The suspension system on the exos is in no way, shape or form "better" than the arc blast.
Every part of the pack is easily replaceable if something happens to break, though it feels bombproof.
In my opinion, not even comparable backpacks.
Sorry about the pictures, not very much light. I'll try to add more tomorrow in my own thread regarding the arc blast.
The Roll top closure is velcro at the top, if you can't tell.