What sort of weight can this pack comfortably...
What sort of weight can this pack comfortably hold? Is, say, 40lb a problem?
40 lbs should be doable. I'd take care in how you pack it in order to comfortably distribute the load.
I've hiked with 40 pounds of gear/food in this bag no problem. Just make sure to put all your heavy items in the bottom/back section of the bag.