In reply to Stew.G: I've got both a Rab and TNF, The rab ones are similar to the old macpac aztec fabric (maybe that's why it's called Inca?) I've found it to be very durable, having kicked it around for the last 18 months, back of car, public transport (buses and trains), planes (maybe you clould get a film title out of its experiences??)
It actually tends to look better for it's age than the TNF did at a similar age, but maybe I shouldn't have bought a Yellow TNF.
Personally, I'll be buying another Rab one when this one dies (if they're still making them then, some of these gear manufacturers are so fickle with their improvements. That's the reason I chose the Rab. I bought the newer version of the TNF Duffle, didn't like the shape so much, bought it used it a couple of times and sold it on).