I've used the great looking Enduro Plus Hydration Pack from The North Face for my last two ultras. It only arrived two days before the Lakeland 100 where it did a great job through 38 hours of effort. I then took it to Chamonix for the 60 mile CCC where it again behaved flawlessly.
It's a very short and squat design that sits low on my back and does look a bit strange when fully laden. However it is incredibly comfortable and I've had no issues with chafage or the pack bouncing. My back bears permanent scars from racing with packs with a longer back length but in 165 miles of racing in extremes of heat and 'dampness' I've not had a single problem.
I like my comforts so had it stashed pretty full for both races but with a bit of work its 9.5 litres should accommodate a very lightweight mountain marathon set up. its just a wee bit small for working in the mountains (bothy bag, first aid kit, spare jacket etc) but I'm finding it ideal for most of my own running and cycling adventures
For me the Boa anti slosh tightening system to secure and compress the water bladder worked as it should but solves a problem that doesn't really exist. Certainly the water bouncing and sloshing about is not something I've ever worried about in any other pack as expelling the air before sealing the reservoir also does a pretty good job. The wire and dial system adds weight and complexity and I had a few issues on the Lakeland 100 when with cold and wet hands kit was snagging on the exposed wires.
I used the mesh pocket on the back for a water bottle on the Lakeland 100 and for my windproof on the CCC and it worked very well being easy to locate with a bit of practice. I find the side pockets on some race packs, which are placed up towards your arm pits, rub against my arms when I'm running but are awkwardly placed when trying to grab a drink or replace your bottle. Placing this feature on the back of the pack makes far more sense ergonomically. On this pack some form of closure would be useful for when carrying gloves, arm warmers etc and a second staggered holder would also be an interesting development.
The included water bladder was very good with a two litre capacity and a large opening. The valve was about average in terms of water flow but it didn't feel like hard work to suck even when working hard and the nifty little magnetic holder for the tube is a great innovation and worked incredibly well. If it's a faff to drink while racing then you won't so little design features like this work incredibly well in the real world. I'm not usually a fan of racing in the heat but coped surprisingly well on the first day of the CCC remaining well hydrated throughout which I can probably attribute to this pack.
The website mentions stash pockets on the chest harness but I think they meant on the waist belt which features two spacious pockets. The lightweight floating harness did get twisted when putting the bag on but once everything was secured then the pockets were perfectly positioned and a pretty good size. An internal loop in th epockets for clipping compasses / GPS would be a welcome development.
The fashion is currently very much for race vests but if you are looking to carry a bit more equipment and like a more traditional pack with some very modern features then the Enduro Plus is certainly worth a look.
Member of the Rab & Lowe Alpine Test Teams & former reviewer for The North Face