Hi mgabb,
In my own opinion, and based on my own experiences, the difference between TrackIR 4 and 5 can be most significantly appreciated in ArmA 2--particularly when playing as dismounted infantry. If you use TrackIR to look around corners, check your flank, etc. when you're playing as infantry, TrackIR 5 is tremendously more stable. Because it requires far less smoothing to be stable, you can perform these kinds of controls much more quickly and intuitively. I enjoyed TrackIR 4 in ArmA. TrackIR 5 in ArmA 2 is on another level. At least, that's been my experience. I've read multiple user accounts that reflect the same. I've even read comments from users that refused to use TrackIR 4 as infantry in ArmA, because they found it too disorienting, and now are finding the same type of control indispensable.
For non-NaturalPoint perspective on this, I'd definitely recommend checking out the
TrackIR 5 thread on the BIS forums. It's massive, so you might be best to just chime in with a request for feedback on the end of the thread. But, if you have the time to wade through it, it has lots of great feedback.
You can also read my
interview with SimHQ , in which I discuss the importance of the new hardware at length, if you'd like more of my own perspective.
The same accuracy, responsiveness, wider field of view, etc. will translate to FSX, but obviously FSX is less of a "life or death" sort of sim. So, perhaps from a competitive advantage or self-preservation standpoint the distinction is less significant. But, for my own purposes, I just can't get enough of the difference in performance. Even if I'm only looking around my cockpit or checking out the scenery below me.
ArmA 2, like ArmA before it, has 4 DOF TrackIR support. This is the same for TrackIR 3, 4, and 5 users. Upgrading to 6 DOF is something that only BIS can integrate.