I'm using Unity on Ubuntu 14.04(.1) and fglrx 14.20 from AMD's site on my Radeon HD 5770.
I've installed Catalyst and enabled its "tear free" setting, which works in that there is never any tearing. (Note: compiz's "sync to vblank" setting seems to have no effect either way- no change in judder when it and tearfree are on, tearing when it's on and Tearfree is off.)
As a test, I'm using MPV to play a 60fps video. In fullscreen mode, it works correctly; in windowed mode, some frames are skipped and others presumably duplicated resulting in an unacceptable skipping and judder.
In other words, the video is being decoded at 60fps fine and the screen is updating at 60, but the frame timing is off- mpv (and anything else) can't present its frame at the correct time. Judder is noticeable in everything from videos to glxgears. XBMC is better than most anything else but it still is not smooth like it is in fullscreen.
This is true for all videos (some, like mpv, are okay in fullscreen- others, like mpv, aren't). Software like RetroArch which provides detailed timing info shows that the variation in frame timing exceeds 10%!
In the very limited testing I did before installing Catalyst, the problem was not present using the Mesa drivers. I can't stick with these though, as the 3D performance is too poor and they don't support GL4 core.
Disabling tearfree does remove most of the judder, but then, as expected, it tears.
UPDATE: I've resorted to using Mesa, which is buttery smooth on the desktop. Surely AMD's drivers don't have this fundamental problem? There must be some way to fix this? Everyone talks about raw FPS figures but nobody mentions frame pacing and compositing jitter.