In reply to Sleepymouse:
Hi. I bought one of these a few months ago. Other than a few family walks and climbs, it's had one big outing (a two day Cuillin Traverse).
The bag feels big for it's size. It just about swallowed a fairly heavy bivvy kit (sleeping bag, belay jacket, spare layers) and harness, rack etc. The side straps hold a rope really well, and the helmet mesh was fine, though I have doubts on how long it'll last (the anchor cords are super thin).
Hip belt pocket is pretty small, but does fit the all important bag of Haribo.
Back system is basic, but I found it Very comfortable. Even fully (over)loaded it felt good. There's not much ventilation, so if it's a hot day you'll get a sweaty back. I'm 6 foot and broad. My partner for the traverse is 5.7 and had the same bag and rated it, so it seems to fit a range of body shapes!
Like all these things, it won't last as long as the 200 quid Mountain Equipment job, but the main fabric of the bag seems sturdy enough. On decathlon bags in general the draw cord and closure skirt fabric can deteriorate quite fast, but the bags still seem to function fine. I'll jury rig the helmet mesh if it breaks as its a great feature.
Just make sure you don't buy the same bag in the same bright red colour as your climbing partner. We looked like Mr & Mrs his n hers!
Cheers
Tom
Post edited at 19:39