$129 for the unit, there is no lag it behaves much like a mouse. The optical tracker follows a reflective dot on your forehead (or on a headband attached to a headset in my case)
There are two modes to its operation, mouse emulation mode and 'trackir enhanced', the latter is the preffered way of using the device although there are not many games out there right now that support it but the Naturalpoint team were at E3 talking to a few games developers. In IL-2:FB you can use the enhanced mode and it really does make the whole sim much more immersive. I've got up in the middle of a game to get a cup of tea, sat down and the unit has still not lost the centre position so there is no re-calibration or centreing. With enhanced support you can map your top hat to something more useful because you'll never use it to change your viewpoint again! it's really intuitive to glance left or right and look out over your wing or over your shoulder or glance up and look over the frame of your canopy. The software is easy to customise and you can alter the axis of the trackir to make deadzones or set it so the pan speed increases as you get to the end of the axis. Enhanced support would be amazing for Aces High or Aces High II.
The mouse emulation mode works in Aces High now, it's pretty easy to set up although it can lose it's centre position easily if you move your head around but you can map a key to centre it to your stick and AH's mouse view mode has a certain 'dead zone' to it so accidental movements are relatively easy to avoid. Many flight sims have mouse emulation and I use my trackir playing Flanker2, Aces High, Strike Fighters and of course IL-2:FB and there are patches to add support for some older games like Grand Prix Legends and Falcon 4.0.
The trackir is easy to use and you only have to make small head movements to pan the view and as I said the software is easy to customise for pan speed. If you look at your monitor and split it into 4 equal vertical zones and label them from the left A,B,C,D...glancing slightly to the 'A' zone could perhaps give you a over the shoulder left view or left over the wing (depending on how sensitive you make it) looking at the 'B' zone might give you a forward 45 degree view etc etc .
