The Murmur is my favorite pack, by far. I even use it when my ULA Conduit will carry a bunch of water easier. This pack is just so convenient for me to live out of. I don't understand the comments about the Spinnaker fabric making you sweat. If you put a foam pad in the sleeve, only mesh and the pad are against the pack.
Regarding durability, I screwed up and did some bushwhacking in mine and got a small tear. My fault. I have used it in temps approaching 100F and yes, you will sweat, but no more than any pack, save an Osprey, Deuter, or REI Venturi; all of which have a suspended mesh panel.
I have done 20+ mile days with huge elevation gains, and the pack handled the initial total weight of 17 pounds well.
My only dislike is the fact I did not read the information on the GG Website of a possible leaching of the mesh dye onto the back of a shirt.
As suggested earlier, this pack is only for those who know it is for them. Also, I got the weight below 7 oz by removing the foam pads in the shoulder straps. Mine weights 6.8 oz.
For total pack weights under 15 lbs, I think this pack is perfect if you can fit your gear in it. I have taped the tear in my pack, and if that doesn't work out, I will be more than happy to buy another one for under $100.