Just to add to the above, I use RAW mode on my D1 which produces 4Mb .NEF files so I get 31 shots on a 128Mb CF card.
File sizes for the D1x increase along with the higher resolution: fine JPEGs average about 2.2Mb and .NEFs are about 7.8Mb in size.
On the subject of transfer rates it is actually possible for the camera to become the limiting factor. The original D1 seems to top out at about 12x - so cards faster than this don't give any write speed advantage. The D1x/h are capable of taking advantage of much faster cards - for example the Lexar 24x cards. Bear in mind that the very fast cards tend to be more expensive so you have to really need the speeds they offer to justify using them.
Canadian photojounalist Rob Galbraith has made a comprehensive review of how the various cards perform in different cameras.