Yeah, it's not really stutters, sorry. It's more like the mouse input gets locked into horizontal movement. When it happens I can't move my view vertically with the mouse (horizontal input works), while moving the view with TrackIR works. To fix it I move my head around or just swing the mouse around until it "releases" and then I can aim vertically again. Sadly, it happens way too often and when it starts happening it's like it gets stuck into this state and it constantly happens, leading me to pause the TrackIR all together.
The choppy view you're talking about when zoomed in I somewhat counter with more sensitivity. If you try the "one2one" setting it's almost non-existent (to me). Of course this means you need to move your head a lot more to look behind you, so I have setup 2 profiles that I switch between depending on the situation I am in. Basically it's the dyslexci profile and the standard one2one profile.
For the Devs: The horizontal locking of the mouse happens more often when I use a profile with more radical movements. If I use the one2one-setting it seems too happen less frequent, but it's a problem no matter what. I'm really hoping there'll be a fix to this.
What I'm accustomed to and what we're expecting of TrackIR, is for it to behave like it does in Arma. To anyone who doesn't know what that looks like - check out this old video: