I've now used the rucksack for six walks and so feel that I'm able to give a fair and comprehensive review. As I wrote in my initial observations, the Berghaus Freeflow 25 + 5 is the best rucksack I've ever used. It's comfortable, rugged, practical, and well-designed. The rigid back is its best feature, preventing objects from digging into me, or rubbing against my back...and cutting down substantially on the amount of sweat I produce; and therefore maybe I'll need to drink, and carry, less liquid.
The 5 litre capacity top pouch distributes the weight I carry high up on my shoulders; the best place for it, both for better balance, and preventing backache. I can put the heavy stuff in there, binoculars, radio, my torch, and a couple of extra bottles of pop...and they're easy to get at; especially by the person walking behind you.
Some other positive features are the easy to release clasps, only needing one hand; two hands are still required to fasten them though. If you've got cold hands or arthritic fingers I think this ease of use might well be very welcome...all the zips have easy to grab looped fasteners too.
The well padded waist band is very supportive to the lower back and holds the rucksack firmly in place, and would probably keep your lower back very warm on cold days - it also holds my map case securely in place, preventing it from flapping about in the wind and almost throttling me.
The shoulder straps are also well-padded, and easily adjustable on the move - so no chafing there.
There are quite large side pockets, elasticated loops to easily store your walking poles, space for a hydration bladder (I've never used one - they seem quite unhygienic to me; and a lot of work to keep clean and sterile) and a pull-out waterproof cover tucked away in a flap at the bottom which I haven't used yet but I'll most likely use it to sit on when the ground's wet; utilising the rucksack as a backrest.
There are one or two negative points I feel I need to cover; they are only minor points though. I've read other reviewers stating that because of the bowed design of the rigid back support this limits the amount of space available in the main part of the rucksack. I tend to agree with this observation, but this isn't a problem for me since I only have my sandwiches, waterproof clothing and a few extra bits and bats in there...and because they're packed in more tightly they don't move about; good if you need to jog to make up time.
Another minor problem I've noticed is that the rucksack is a bit unstable when it's full and placed on the ground; it tends to fall over. This is a particular drawback for myself since I travel on buses and trains all the time and it gets in the way, blocking the aisles - I also have to make sure that I clasp the waist band together otherwise people have tended to tread on the 'wings'...at least the clasp is easy to undo when I need to get off the vehicle and put the rucksack over my shoulders.
One final problem I had, which was probably my own fault though for not properly configuring the rucksack to my body size, is that a stay on one of the shoulder straps has already come unstitched: it doesn't seem to affect the usability of the rucksack though.
Overall I'd say that the Berghaus Freeflow 25 + 5 Rucksack is a very good general purpose rucksack for day hiking, either on your own or with friends; comfortable, well-designed and well-made, practical and easy to use...what else could you want?