Let me see what I can answer.
so what is it all about, does it work?
-It's a plate you mount on your non-Line skis or any ski without Lines quick mount system. Its just turning screws to put the Reactor on the plate.
do you need a shop to get the plate mounted?
-I'm not totally sure, but I think not.
does it only work with lines?
-Nope, its mainly used for Non-Line skis so you can use one pair of Reactores on many different skis
do you feel the plate while skiing, due to the thickness of the plate?
-Don't know, never rode them, I'd imagine not a whole lot
can you still cross your skis without touching the plate?
-I cannot honestly see a reason why not, I mean its mounted under your boot and binding.
how are the reactors anyways?
-Every review I've heard, sketchy, ride them for yourself before you go and spend money on the and the Freedom plate.
I could be wrong on some of those but I'm pretty confident thats my best opinion of them I can give you without owning them.
Go there, its a PDF document with a whole bunch of FAQ's about the Reactors and the Freedom plate.
Stay Classy Newschoolers