Definitely use a good card reader as Kirk suggests. BTW see
www.robgalbraith.com for speed comparison of different readers. The Sandisk Extreme series, especially the firewire (which is great on a mac - unless you happen to buy the new aluminium MacBook, which sadly lacks a firewire port) are fast, rugged and reliable. On a Mac firewire is still quite some bit faster than USB. Or the Lexar pro series, which allows stacking of several readers over firewire (although, with four - the maximum supported - Firewire 400 can get saturated with fast cards, so even though PM allows for ingesting of several cards at once, the speed might drop a bit when connecting three or four of these to the same FW port)
If you need to ingest from a camera directly, you must set somewhere in the camera settings the USB connection type from PTP to Mass Storage protocol. PTP is only for controlling the camera connected to computer remotely, Mass Storage allows the card to be seen as normal USB drive.
It is hidden somewhere in the settings, can't help here as I no longer shoot Nikon.
Frantisek