i sent a 300D back due to a manu. defect (the foam that catches the mirror started shedding in the body!?) they fixed it and returned it but there was still sh!t up on the focusing plate, so i sent it back and they replaced the focusing plate, but when they did the sticker with the focusing marks on it was blurred and off, so i sent it back again. Overall I spent 1 year sending it back, and had to call canon corporate offices - got a hold of one guy who I worked with for about 6 months of the 1yr and finally I just said, look I want to use my camera, how about after this next time you just give me 1yr extra warranty and if I have any problems I'll take care of it later.
The service was fast every time and once I got a hold of corp offices my shipping was paid for both ways, the only thing that bothered me is that they refused to replace my camera with another one and insisted on repairing it every time. The last time I sent it in it was all fixed tho, there was one piece of sh!t on the focusing plate but I don't care it doesn't show in pictures. Been using it for 2 years now without problems, and hoping to upgrade to another canon soon.
I think I just got unlucky cause I had never heard of anything like that happening before, my uncle told me it was really weird and is a major canon user in his profession.