I use TrackIR 5 and wouldn't want to fly without it anymore.
I have had to manually adjust the curves in all games to make it feel more natural. The original curves have too much of a dead zone / slow zone in the center which was the main problem for me.
Once I tweaked the TrackIR settings / curves, it feels very natural and definitely gives me an edge as I can quickly look around the cockpit in a natural way. Keeping your eyes on a target while doing maneuvers, for example, becomes so much easier when you use TrackIR.
The more I use it, the more natural it feels, and often I find myself trying to use my head to look around in games that don't support TrakcIR.
