I agree with GoodFinder.
I just put the AutoPower race roll bar in my WRX on Saturday. It is easy and inexpensive, but somewhat time consuming (3 hours of pulling, pushing and gentle persuading). Two of us did it - I'm recovering from shoulder surgery and my friend is recovering from flu - how hard can it be?
I'd put my trust in a roll bar before I'd assume that I could "duck" (I can't because of my harness) or be able to hold my head close to the B pillar (I couldn't because if the car's rolling/flipping - God forbid - I'll be trying to keep my head attached to the rest of me).
I followed jamz excellent installation instructions. Except I forgot to loctite the double nut arrangement AND put those nuts on the inside of the rear wheel arch and not inside the car. I didn't realize this until after I sprayed the undercoating - whoops! I'll play it by ear and see what happens after my first session at Laguna Seca.