Boy do I have a story for you!!!
First of I have owned 25 black cars over the last 8 years. Its safe to say that any car painted black is the best the car can look. Most of these cars were cadillacs, jaguars, corvette, etc. I currently have a black on black XLR. So, I am VERY experienced with black paint and how to properly take care of it.
Without a doubt the best black paint job I have ever seen was on my 2000 corvette convertable. Not only did it look great, it held up very well. There were on scracthes or swirl marks on that car and I sold it 4 months ago when I got my XLR. Because the XLR is built in the corvette factory, I was hoping for the same results. However, that has not happened.
In 1998 I bought a new Cadillac Deville Concourse. Great car! However, soon after delivery I noticed swirl marks in the paint. Dealer said, "no problem, we will take care of it at next service" Okay. Long story short, the car went back 4 times in the next 2 months and the swirls kept getting worse. Finally, I demanded to talk to the regional rep for Cadillac and she agreed (after a lot of fighting) to re-clear coat the car. I was advised by a body shop friend not to do that. (the swirls in black paint are really small scratches in the clear coat and can often be buffed out) Re-Clear coating the car is a fancy way of saying repaint the car. It took 5 weeks to get the car back. So, in my first 4 months of ownership, I actually only had the car 3 weeks to use. They told me that the paint was "soft" which caused the problem. That was pure BS. ANyway, after I got the car back all was fine for about 1 month and the problem came back. As part of my deal I reached with Cadillac when I agreed to the re-clear coating, if the problem came back they had to replace the car. They did, only they wanted me to take a white one! I refused. The second car was great and I never had problems with it.
So, when I got my XLR home I took a good look at it. Guess What? Swirls. However, I am much more experienced now and simple fixed it myself. The guys at the local Cadillac dealer are butchers with the buffers which can easily cause swirls and if you are not experienced every time you try to fix black paint you will simply make it worse. Take your XLR to an experienced body shop guy and he can take them out and it does not cost much. Also, NEVER was you car in a car wash.
Hope this helps.