Fast Glass,
I have a 1DIII and I upgraded my mem cards to 150 MB/s. When I did this I almost doubled the # of shots before buffer full. I used a SanDisk Extreme Pro for the CompactFlash 160 MB/s card and a Lexar Professional 150 MB/s for the SD card. I have not had any issues with my cards. I think at the time I went with the Lexar to save a few bucks. My thinking was if the card fails I have a backup in the SanDisk.
Cheers
Mark