Thanks for your help Ryan! I managed to get the ADIS16448 example to work using interrupts instead of constantly reading the registers and coming up with a pseudo-dt. Check out the code here:
https://github.com/juchong/ADIS16448-RoboRIO-Driver
And if you want an IMU to play with, get one here:
http://firstchoicebyandymark.com/fc16-115