Hi Jonas!
You should also know that not all of Tobii’s eye trackers are compatible with EyeX SDK, depending on whether they use ip or usb protocol. See respons http://developer.tobii.com/community/forums/topic/tobii-eyex-engine-compatible-devices/#post-2171
I ended up using the Gaze SDK, and it have worked fine for the most. But if you can choose EyeX, you pretty much get calibration and gaze data filtering for free.