I have never ridden Flows, but it seems like one of those things people either love or hate; there seems to be no in between. Riding with friends who have them, the one drawback that I observe is getting into them when you are off piste on steep terrain; the highback does not want to stay folded down far enough to get your boot in. They seem really good for well groomed areas where it is relatively flat. On the older Flows, I can see where a leash might have been handy since there cases of them popping open. I think they have long since fixed any issues like that though.
But I contradict!
Anyways, I'm going into my 2nd season of boarding, and bought FLOWs (Amp 9s) last year (1st season).
As Snowolf pointed out, they are a bit of a pain in steeper areas, and also aren't the best on powdery areas. You actually have to somehow flatten out a section before you can stand up to get in, otherwise you sink entirely on a diagonal.Putting them on while sitting down is a no-no. In deep, I think you'd be able to kick your foot down into them while on your knees looking up the slope.
I'm going to be heading out west this year and can let you know what it's like in real powder, but until then...
Dialing them in isn't a huge problem, and they are fairly comfortable (no pressure points). To be honest, I did it at home last year with my boots on, and then didn't change the setup for pretty much the entire season. Time wise.. not a huge save in my experience, cause if you get some ice build up over the plate, you're still gonna be kicking your foot into the binding at least a coupla times.
I think the hate is because older Flows were...well...kinda crappy, or at least looked/felt that way.
I don't believe my Amp9s are anything special, but their NTX lineup looks very promising.
With regards to their back opening up... not so much on the new ones. They actually clip shut, unlike the older ones that only used the tension of your foot or something like that.
For what it's worth, I am considering strap ins as my next binding, but I think I can get at least 2 more seasons out of these comfortably. Then we'll see. If I can try their NTX line, I may stick with Flows in the future.