Watch out re:SPI
Last year (2009) our team bought SCA3000s from sparkfun(
http://www.sparkfun.com/commerce/pro...d=8791)--wired them up to a a different device and had them working nicely with SPI...Gave us AMAZING accuracy btw..
Then we took them to the cRIO and started using the standard WPILibs...and we got junk...some careful work with a logic analyzer and oscilloscope revealed that WPILib's SPI library was reading the data at the wrong point on the wave, and because the Labview VIs for FPGA control are all locked we couldnt fix this. Further, our custom library(that worked on a DAQ, albeit a little slowly) for SPI was pretty much useless because we couldnt get microsecond precision timing to do the wave generation, and once again the FPGA was off limits...
I doubt the same problem will come up with I2C, but this was really sad for SPI...