I have the relatively new Nikon D3100. But as far as I can tell, it doesn't support the new UHS-1 transfer standard that the ($75/16GB) Sandisk Extreme Pro uses to get its 45MB/s rate.
In fact, I've seen from two sources that, when used in a non-UHS-1 device, it actually performs a little slower than a non-UHS-1 card. I.e., the ($45/16GB) Sandisk Extreme SDHC (rated 30MB/s).
This is pretty interesting, because the Extreme can be a lot cheaper.
(NB: The only data I've personally observed is that an Extreme Pro way outperforms an Extreme III (rated class 6) in the D3100. So of course, this doesn't help answer my question.)
tl;dr - Has anyone compared an Extreme vs. Extreme Pro in a non-UHS-1 camera?