I have ran some experiments on the TWR board and achieved 1.3MB/s of write performance on a SDHC Class 4 of 4GB. The experiment was run from a task inside of the MQX RTOS.
Whould you have any performance measurements made on other Freescale's MCU or even on Kinetis as well?
If you have any ideas of how to increase the write performance, please, tell me. My application requires 2MB/s of performance.