I had it fitted to my Z4MC for a while (i.e. until I had the little lorry scrape), and it protected well enough against stone chips. I had the bumper, 30% bonnet, wings, mirrors & lenses done - probably cost about £700 including fitting.
My instructions were simply to wash & wax as normal but to avoid any of the 'industrial-strength' road film removers as they eat the plastic. It does seem to attract bugs more than paintwork though and you have to be careful with what you use to remove them. Any discolouration you get with the film is usually superficial and the company will buff/clear this for you under the warranty.
Was told I could buff it like the rest of the bodywork too.
I only took it off as the insurance company refused to pay out for it's replacement as I'd not declared the modification
Might have it refitted once I've had my respray next year, but will probably go for the full bonnet kit rather than the bikini one as it covers the whole lot and makes any mismatch in washing technique less visible