Hi Normog, I fitted the Librands rollbar to my previous car. Its not difficult but takes some time. Access to the parcel tray is good, not much space lost. Paint on the subframe was pretty poor. I would think the exposed parts of that (on the chassis) could rust in time. I thought the hoop itself and its flanges where a little thin. I would have prefered heavier gauge material.
The height is low enough to fit under the easy-up hood, and as jays says it might not keep you out of harms way completely but I still think a good rollbar improves your chances in a roll significantly. (and also adds some side-impact and torsion stiffness?)
For my current car I am thinking of a slightly higher custom made one, together with a harnass.
Cheers J