The K2 auto is a light binding at it works well. I used the pre recall binders which worked fine. The recall had to do with an issue where you could step on and fray the cable causing it to break. At least that is my understanding. If that happened the whole system was done. Supposedly they have fixed that. As far as ease of use, performance, and comfort goes. It was a very high quality binder. The only question I had was durability. The recall seemed to support that. If that is fixed, it should be a great reliable binder. Very easy to use.
The Flow Team binding is the lightest out there I believe. I've demo'd them and they were ridiculously light, yet very comfortable and responsive. Also very very expensive. If you don't have a hook up or a huge supply of cash I would look elsewhere. The NXT models are nice too.
Rome, Ride, and Union all make quality bindings that don't weigh a lot. Especially when compared to the Cinch. That is a freakin' medicine ball of a binder. I have a b pair of Union Force DLX binders and for freeriding they excel. Nice and light, very comfortable and super responsive. When I demo'd them I liked them better than the Rome bindings (Arsenals I believe) I demo'd and much better than any Ride binding. Sorry, I am not that impressed with them. Quality, yes, but so many other companies put that extra effort into their binder. They could step it up a notch.