There's a reason snowboard bindings have stuck to a two-strap design for the past 3 decades. The FLOW's looked like a good idea, but ultimately they were more difficult to get in/out of than regular bindings.
1.) They are impossible to get into while sitting down because the back has to fold down in order to get your boot in. Strapping in standing up is only remotely possible on the flats, so you're screwed if you have to strap in/out on the slopes.
2.) The highback needs to be super-stiff to accommodate the clamp mechanism, so if you're into a flexy binding, you're out of luck.
3.) You have to exert a good amount of force to clamp/unclamp the highback which is in an awkward position, so you better have a good chiropractor.
4.) You still need to adjust the foot flap to get a correct fit, so the clamp just ads another step to the process of getting strapped in.
5.) The foot flap is nowhere near as responsive as the traditional ankle/toe strap combination.