We are very aware that eye tracking today is not pixel-perfect, and that it probably never will be. But we have seen it proven more than once that a good user experience can be created based on the current accuracy and precision in combination with a user interface designed with eye-gaze interaction in mind. The point is that it takes something more than high accuracy and precision to create a good user experience with eye tracking. This is how one of my collegues have put this:
When creating interactive applications making use of eye tracking for the general public, a core concern for any developer should be the consistency of end user experiences. A natural, effortless and magical user experience that works for one person out of twenty can be an interesting concept at most. One that works for anyone will change the way your users interact with computers fundamentally.
Historically, one of the core metrics by which eye tracking devices have been measured is so called ideal accuracy and precision. This is defined as the best accuracy/precision measured for the most easy to track user. In many cases this is an interesting benchmark, especially within research where one could try several test participants before finding one that it works on. However ideal accuracy and precision gives no information of how often you will see this level of performance for a random user, making it much less useful as a metric for interactive applications using eye tracking.
For developers of interactive applications that are intended to be used by any user, focus should rather be on how consistent the end user experience will be over time, during movement, in varying surroundings and between different users.