If you are using for a router table plate, Bill Hylton in 'Router Magic' says that polycarbonate is not maybe as 'sag resistant' as acrylic or phenolic if you are hanging a big router from it. Having said that, I bought a piece of polycarbonate from Rockler when I was on holiday last. Haven't bought the 1/2" router yet though!
Anybody got any experience of polycarbonate for router plates?