I’ve had a Catalyst for over ten years and have used it on quite a few long walks including the GR20 in Corsica (a good test for stability) and the TGO Challenge and have always found it very comfortable. The latest version has several changes from my original model. Firstly it’s now available in either Robic fabric or heavier Cordura. I’ve tested the Robic one. This fabric feels a little stiffer and more solid than Dyneema. The mesh on the pockets feels tougher too and should resist abrasion and tearing better (there are several holes in the mesh on my original Catalyst).
The key to the comfortable carry of the Catalyst lies in the fairly stiff back and the wide, well-padded hipbelt. Together they are very supportive and easily handle 18kg loads (the maximum recommended by ULA). The pack is very stable too, as I found in Corsica.
ULA says the volume is 75 litres. This includes all the pockets and the extension collar however. The main compartment is more like 50 litres (ULA says 42 but I think that’s an underestimate). The pockets are very roomy though and I found the Catalyst suitable for a winter trip in the Cairngorms with fairly bulky gear.
The Catalyst is quite expensive compared to alternatives but it is one of the toughest packs tested and should last well. It’s available in the UK from Ultralight Outdoor Gear