I have a TrackIR3 Pro with Vector Expansion. I've tried MANY times to get used to it, each time over a period of several days.
But I can't! I'm slow and innaccurate with it.
In real life, you look at what you want to look at, even if your head or the car moves. Your eyes automatically compensate. With TrackIR, you use your head to look around, but your eyes stay focused on one place. I can't get used to it, no matter how many profiles I download off the net, and how much advice I get off people.
GTR was the same, although I did quite like the head lean function.
Flight sims are plain (no pun) weird too.
I'd personally say give it a miss, but most people here seem to have had more joy with it, so perhaps it's my brain at fault. Am considering selling them on eBay in the not too distant future. What would be a good price? The downside is I'd quite like to keep the Vector Hat (although not the clippy thing).