we have worked on couple cars with ceramic clear (BM S600, E46 M3, some others, C5 Z06 corvette have some kind of ceramic clear but its a lot harder then euro ceramic clear). it is harder to scratch but its even harder to fix.
now there is alternative, i am getting new product to try on my car and on my friends car for now before i can put it on other cars. Product called CQuartz, its nano ceramic coating which looks like just as hard as ceramic clear if not harder but only good for about 2 years. im putting it on my honda accord becouse i cant wash the car without marring it even with 2 bucket method.
here is link (im in no way associated with the company). it is A LOT cheaper then reclearcoating your car too
http://www.aquartz.net/aquartz.html
here is couple videos of the product
please do not try to do what they do in video on your car
http://www.youtube.com/watch?v=hg1XK-fy3AM
http://www.youtube.com/watch?v=O0dTY1_Iebc
there has been products like this in past (one of them is Optimum Opti coat) which has similar properties but it was not avaliable to public, only pro detailers could order it. and it was complicated to apply, this products seems a lot easier to use, this is why i ordered it
Mikhael