Vincent, I'm sorry to say that while all those games can "claim" to use TrackIR in a first-person mode, none of them have in my eyes made such a thing practical... with the exception of Armed Assault.
Insurgency, last I checked (which was some time ago), had a big flaw in there implementation. That being if your head wasn't completely centered, your aim would not at all be accurate.
Americas Army... LOL at that. All it is at this point like trying to play with the mouse emulator on. I actually think the mouse emulator has more features than AA's implementation. Let's just move on...
World War II Online, I will say you can actually use this.. but it's pretty shallow. Infantry in WWIIOL by default have the Q and E keys to look in the 10' and 2'oclock positions. With the TrackIR, this doesn't change... which is strange because in any vehicle you can look in nearly any direction. This causes problems because you have to turn your head at the max limit to only get as far as 10' and 2'.
Armed Assault is the only saving grace in this genre. Their implementation was nearly perfect, apart from a few minor things. Although everyone seems to have their own preferences, I DO use all 4DOF (Pitch, Yaw, Zoom, Lean) and have no problems using TrackIR to lean or zoom. It is a shining example of how FPS games should be doing TrackIR in the future.
It's not a perfect system, mind you. Poor tracking will cause the view to snap to center the instant it loses the IR dots. When this happens a dozen times a second, it can be very annoying. I repositioned my TrackIR closer so that issue stopped with me.
Leaning is good, but it's slower than using the keys. It can't be too sensitive you'll accidentally start leaning while running, causing you to switch to walking. I have my X traverse (leaning) axis set to an aggressive curve and that usually stops keeps this from happening unless I need to recenter.
I use Zoom with the TrackIR as well, but I think most players prefer to use the right mouse button. Unless you are used to it and can control it, it can sometimes be difficult to zoom into a specific point smoothly.
For a future FPS game, I would like to see forward lean as well. I think it would be much more intuitive than zoom. Perhaps it could be a feature of ArmA II? we'll see.
