For the most part, it works much the same way as wood or mdf moldings. It is a little more fragile, and can break easier, just make sure you use at least an 80 tooth blade in your chop saw.
You can use an air nailer, just set the pressure down or you'll shoot right through it.
NEVER use a butt joint in a long run, whether you're using wood, mdf or plastic. Those never turn out as nice as a mitered joint, always more noticable.
I tend to just mitered inside corners more often, especially when painting. Coping just takes too long. I usually only cope when the corner is too far off and leaves a gaping, uh, gap.
Just use plain old paintable caulk for all joints and nail holes.