I have to say, I have only ever painted complete cars in celly .... bar my wifes bumpers which she is forever smashing. Over the years had no problem with it. Good quality, high gloss thinners and plenty on and you can achieve good results.
My last 3 cars have all suffered from not going off properly. I am convinced the activators once used have been altered, left out or something. I am pretty miffed with it to say the least. It does go off eventually, but can take months .... months that if you use the car, can be to the detriment of the paint job. Similarly, if you get a car in and have to sell it, you could be faced with a comeback!!