I haven't got one for my GP but I have had one for my 323 since 1993. I brought it back from Canada with me.
I do find it useful in stopping stone chips and mashing the flies before they hit the grille. But I don't leave it on and my instructions tell me not to leave it on if wet.
I did find early on that the corners were starting to chafe the paint. So I use masking tape under each edge now and take it off after each journey.
As the car only goes to shows this is not such a ball ache.
Why not try that 3M stuff (like thick cling film) that sticks to the car and is supposed to keep off stone chips?