As I'll say to anyone who's getting going on TIR, spend the time tweaking it. It is the single most personal setting you can have in this game IMO. Even moreso than joystick mappings. I spent about 2 weeks when I first got mine messing with things until it was where I want it.
+2
I'm still getting used to TrackIR and I've been using it nearly a year now. I still find I'm faster/more precise/etc with the thumb hat, it's been a real trial trying to wean myself off of the "old" way, but it IS slowly coming. I flick TrackIR into pause mode when I get into fights still, but I've found myself doing it less and less in fights at certain times, and find at times it gives a big advantage in seeing "up" through the canopy at a plane I'm fighting when the canopy bar through the center/top of the canopy in many planes is blocking the enemy plane from sight using the "thumb" way.
Due to the fast paced nature of close range fights in Aces High, this is the nature of the beast for Track for me - stuff like Falcon BMS, DCS sims, and other such games, it isn't quite so tough to use TrackIR for me.
Skyyr has really good advice on using TrackIR, I'm not sure where it's posted, but his settings and method is the best I've found so far, although Mace2004 had a great starting place for players new to head tracking too. Skyyr's is a lot more of an advanced method.