Nick:
I agree on the transend cards, I use the 32 and 16 400x cards, without any issues. They are not "blessed" by Phase One however so I did not mention them. I agree great card, fast no problems in 2 years of hard use.
The only transend card that my One back seems to not prefer is the slower 132X (red card colored card). This card does tend to get hung up at times so I no longer use it, Nikon cameras love it however.
Paul