I recently used the Zaino products on my black Crossfire. I have a before and after picture of the swirl marks that were on the drivers side rear column.
http://www.baddass.net/autos/index.htm
Check the first two pictures. I had some horrendus swirl marks that really showed up once I washed all the previous wax off (they also looked pretty bad previous to me washing the wax off). The hood was probably the worst looking part of the car. I applied 2 coats of Z-5 (supposedly made for filling in swirl marks and fine scratches). There is a significant decrease of visible swirl marks. I can only see them in direct sunlight. Sometime soon I'll probably do another coat of Z-5 and finish off with Z-2. I'm pretty happy with it, so far. Hopefully it won't wear off too soon, because it is a pain in the rear to apply multiple coats.
I have no doubt that Crystal Guard works very well, with minimal maintenance being an added bonus. My issue was that the car had swirl marks from the moment I got it, though they were minimal. I'd rather spend my time waxing it, now that I've seen the results of the Z-5, than get a detail shop to use a buffing compound to remove them. Such is the plight of the black car owner. We have to sacrifice time and work to get our cars looking their best, but when they do, they look awesome.