After I got my D1x I picked up an extra battery, 2 1G IBM microdrives and 1 256K flashcard, an AC adaptor to open the mirror for CCD cleaning and a firewire and card for my PC. Total cost of these add-ons was about $1,100. I also spent $500 on an Epson 1280 printer.
I do action sports and other outdoor photography. Even though I am very careful when I change lenses, CCD dust has been an occasional problem.
You will need CCD cleaning supplies. I had no luck removing dust with a bulb blower. There are very good cleaning instructions on this forum. Sensor swabs and Eclipse fluid really work. The swabs aren't cheep, about $45 a dozen. I had trouble finding them locally and got some from The Filter Connection @ www.2filter.com.
All of my lenses have worked perfectly, the pictures have been great and I am very happy with this camera.