I think it could make a difference...
461 meg PDF copied to the sd card via my MAC and then back to the hardrive
Standard Sandisk SD card (Non SDHC)
1:26 write
0:45 read
PNY Optima Pro SD 20gb/s 133x (Non SDHC)
0:34 write
0:23 read
the write was ~3 times as fast and the read was ~2 times as fast