I haven't had a chance to take it on a nice long hike/float yet, but loaded it up for a short paddle on the Willamette River in Portland this weekend.
I was able to fit boat, PFD, throw bag, smaller dry bag, and raincoat all in the large waterproof bag. Extra straps are included to help configure multiple combinations of strapping paddles, PDFs, ect. to the outside of the pack, and I think this pack holds great potential for winter ski touring trips as well.
The heavier weights of a packrafting load (especially on overnights or multiple day trips) have made for uncomfortable trips in the previous packs I have used, but the bomber hip belt and back panel already look to make those trips more comfortable.
I've been working with Six Moon Designs (SMD) over the last year as their media manager, and used SMD's Fusion 50 on the CDT this year. The Flex uses the same suspension system as on the Fusion 50 (I often carried 6-7 liters of water and 5-7 days of food...probably around a 40-45lb load at times), and was very comfortable.
We are looking forward to putting this pack to the test!