I'd get them because I liked them and they fit my needs. That's normally why I buy stuff anyway. I don't own any Flows, but a buddy of mine does and likes them. The biggest advantage is ease of entry. The biggest disadvantage is that if you're trying to get into them on a steep pitch, it's a huge pain in the ass.
As mentioned, the best part about flows is the speed of getting locked in. The one time I tried flows, I was able to strap on just before I got off the lift. What I didn't like about the flows was the response. To me, it didn't respond as well as the Targas I ride. However, this may have to do with the setup of the flows as they weren't set for me (it was a buddy's board and we swapped for a couple of runs).
Which wire are you talking about? The thick one at the back? That lets you set the highback angle.
As for why to get them... I have traditional 2-strap bindings and flow bindings. The flows are harder to set up properly the first time, but after that it is lock-and load each time. Unlike 2-strap bindings, you don't have to fiddle with them each time you get off the lift to make sure it isn't set too tight or something.
Flows can be tricky to get out of when you're dead tired and don't feel like bending over. I like mine. They hold my boots.