I have free track w/one point tracking. It works very well for the price. I don't use it for realism, i use it for functionality and performance. It does take some messing with to make it work correctly and smooth. Other more expensive and probably better solutions like TrackIR I would imagine would work better 'out of the box' because of standardized hardware and faster polling rates then a cheap webcam. With free track it can be hit and miss since almost everybodys equipement is more then likely different in some form or fashion. I put my free track together for 10 US dollars. I had a friend that owed me a favor that had a webcam new in box (microsoft vx1000). One infrared LED, a AA battery holder and a molex connecter from radioshack. I use the tube from a BIC pen to hold the LED and attached the female molex connector to the end. The other molex is on the tip top of my headphone set and the battery holder is mounted on the side of the headphone set. This way I can plug in the LED pen, if you will call it that, to the headset and use it for LFS. This way I can turn it off easy and not have to worry about being in the way during non LFS activities. I tried the hat, but that was annoying to wear.
Hope this helps.
Good luck!