I've had a freeflow pack for a long time. In fact it was one of the first generation versions and I used it for a long time. It's still in the gear cupboard it's just been superseded by my gear obsession.
The current version has changed slightly but the concept hasn't changed. The mesh grid along with the curved panel allows the ''free flow" of air to the back meaning less material pressing on the back whilst you get hot during activity.
The 25 + 5 version you see here has a lot of nice additions - netted pockets, vented "EVABREATHE" shoulder straps and a hydration pocket to name a few.
The pocket on the flap has a bigger opening with a curved zip opening.
The biggest addition I can see is the BIOFIT system which is an adjustable back height. It has 5 settings from XS to XL allowing it to sit correctly around the waist which it does. It sits comfortably over the shoulders and around the waist. I did find the waist belt loosened off a bit but nothing too serious.
I find that between the mesh and the curved panel is good for stashing my map whilst walking.
The additional features do add to the weight of what is an already weighty system. Granted its not the lightest but it carries well, so a balance is struck.
There are walking pole attachments which can be bastardised to accommodate an ice axe.
I was a bit concerned about the white straps getting filthy but after several lanes on the hill it has returned still white. Obviously just aesthetics.
There's also a rain cover, which I always completely forget about.
I do have difficulty with the volume of the pack. the knock on effect of the curved panel is the main area has to curve too. lt doesn't however have an adverse effect on the packs centre of gravity. What it does affect though is how the pack holds its contents. To me it feels restrictive, the curve seems to impair access to the depths of the sack. Not majorly but enough. And it doesn't feel like it's the full 25 litres.
It doesn't make it a bad pack. Actually its very comfortable which is the main thing. It makes a good summer and pre-winter pack.The side pockets, which I assume are the + 5, are really handy. Normally I keep a water bottle in one and water proof trousers in the other so they're handy.