Rono, I hope that someone can tell you straight up. If they can't, you need to do some Google safariis and try to find out what the write-speed of your camera is. I tried this for my cp 5700 for the same reasons and couldn't find out. I even asked Nikon tech support and they wouldn't give me a straight answer. If you do manage to find the 7900's write-speed, then you have to check out the memory card you are using for it's read-speed. Try the literature that came with the card if you still have it. If not, put your safarii hat back on.
In theory, all you should have to know are the write-speed of the camera and the write-to, or read-speed of the card. If the camera can write faster than the card can read, you could benefit from a faster card.
What I've actually heard is that real-world performance of a given card with a given camera is uncomfortably close to voodoo. A card of a rated speed can operate differently depending on the brand of camera you use it with. Something about the chip architechture being more compatible with some camera brands than others.
If you have friends that also have digital cameras, maybe one of them has a high speed rated card compatible with your camera. If so, ask to borrow the card for a few minutes, stick it in your camera, reformat it and shoot some test pix to check out the delay.