Despite having fix 60 FPS, random stuttering occurs while looking around with TrackIR. The video linked below (watch in fullscreen) demonstrates this well. (On YouTube, you wouldn't be able to see the problem because of its 30 FPS limit).
https://www.dropbox.com/s/s6apdpp1th3v4by/Launcher%202013-07-08%2012-58-06-98_x264.m2ts
In the begining of the video there is stuttering, then after around 8 seconds it stays as smooth as it should be. It happens with every game I tried so far (IL2 CloD, RoF, DCS, ETS2, Arma 2-3, Race07).
I've been browsing the forums for weeks now, I've tried all the settings suggested for similiar problems, but it didn't help. Don't have this issue with GTX680/670 or HD7970.