I use my TrackIR 4 in LFS and I wouldn't be without it.
For me, I found the optimum way to use it is to program a button on my wheel to 'enable' and 'disable' it.
When it's disabled, the veiw snaps to the dafault LFS view. When its enabled I turn my head to see what I want then disable it again.
I don't use it for cornering very often, but it's invaluable when there is another car close to you and you want to look in that 'blind spot' to see where they are... You can hear them, but without trackIR, you can't see them.
45 degrees of instant head movement is ok, but it has it's limitations.
It took me a while to set the profile the way I wanted it, but now I can't race without it.
Best add on for LFS for people that own a wheel and don't have the space for a 6-DOF platform.
strictly IMHO of course...