I kept meaning to post a response now that the Ultimate IMU has been released... and I hate to be negative here, but the product is very lacking IMHO.
First is the issue of the price. Sparkfun has painted themselves into a corner on the price, because the Razor IMU costs only $125 and has very similar hardware capabilities. So anyone looking at IMUs is going to compare the $200 price of the Ultimate to the much lower price of the Razor and wonder, WTF?
The next thing that bugged me was the product page for the Ultimate was almost entirely devoid of any helpful information. Please take the time to create a datasheet, user manual, etc etc for a product of this cost and complexity.
Lastly... the firmware. I poked through the firmware and did not see any Kalman filtering or anything else of significant value going on.
My personal decision at this time would be to pick up a CHR-6dm simply because it has the important feature (Kalman filter) while the Ultimate only has some nice convenience features (USB connector, SD slot, XBee connector) ... Of course that could be rectified with updated firmware.
Rant over, we now return to your normally scheduled programming