Hopefully I can bring some industry experience and an honest appraisal for you.
To be clear from the start, my company Morethanpolish Ltd is the UK Distributor for a Belgian Ceramic coating, Kenolon Ceramic Shield, and my other company Race Glaze Ltd markets its own 9H Ceramic product.
Are the promises correct or exaggerated - depends who you listen to ! Its definitely the hottest new thing and there are people peddling dubious products at huge prices. The key is preparation. Any defects under the coating will be magnified, not hidden like wax will.
Are there different qualities - yes. Hardness is one measure - 5, 7 or 9H, but quality and credibility of supplier more so. And quality of application company. This dries like glass and has to be wet sanded off if applied badly - and some are. We run a national training and accreditation scheme for Kenolon so all our guys will do a perfect job. RG 9H is optimised for DIY application by intelligent people (or who can at least read and follow instructions).
What is a reasonable price to have it done - expect £300-400, plus the prep - at least a single stage machine polish.
Does it mean no more waxing - yes. You can wax if you wish but no real point.
Have any of you had it done and if so what do you think - had a panel done on my old P-car as none of my other cars paint is good enough (see above). But I have witnessed and helped apply on about a dozens training courses as well as being trained myself. The Ferrari Centre have a test F430 bumper, which they invite customers to hit with a marker pen. The uncoated side marks, the coated side not.
Durability - we'd expect 30-50,000m, so for cars like Ferraris, much longer.
Shine, beading - outrageous !
Hope that helps.
The Kenolon network is shown here if of interest:
http://morethanpolish.com/kenotek-car-care.asp
RG 9H here:
http://morethanpolish.com/Race-Glaze-9H-Ceramic.asp