I have a black SP. It's still black and unmarked. Got it when it first came out for my birthday. As far as I saw from my brother's handling of his SP, the SP only takes a beating when you don't handle it appropriately.
The only problem I had with the SP was that Nintendo decided to release a BETTER SP with a brighter lit screen late into the GBA's life. Years after the SP's release and right as the DS was starting to gain steam.