Just thought I would give you a layman’s perspective since I just got to try Tobii’s product for the first time yesterday at GDC. I walked up to half a dozen game demo’s and all of them reacted to me but it was clear none were calibrated. For example, all games I tried had a feature where looking towards the edge of the screen would cause the camera to drift slightly where the user looked. This worked well when without calibrated. Most of the games also would highlight HUD or game elements when looked at. This was very sketchy without calibration, leaving me wondering what was even supposed to be happening.
My observation is that very general tracking seemed highly likely to work when a layperson just walked up but precise tracking was not at all reliable.
After trying the demos without help, one of the presenters showed me how the calibration worked. It was very quick, intuitive and only took a few steps. After calibration the trackers were very responsive and accurate. I was very impressed with the experience after this point.
If calibration were integrated into the program, I bet it could be done in under 30 seconds with very few problems. The only downside is that it would require the user to know that it needs to be done and do it.