I use it, and I love it when it works. Only problem is that sometimes it does lock on, but the shot goes flaccid and ends up flying a parabolic curve without even bothering to track the target in the slightest, even though the aircraft is hardly moving. I can't say how many times I've tried shooting a transport that was just 50m away, just to fail multiple times and waste my ammo.
On one occasion I shot at a gunship that was not too far away, hit with both missiles in my first volley, he didn't die (not that I expected him to, it usually takes 3 missiles) he flew off to go get repaired and I shot as he was flying away. About a minute later I get two kills. The missiles apparently followed him most of the way across the map.
Also, I don't know how to explain it, but I feel that I've had more luck with the SAAW when playing on the EU team. I think it fails to track less often, for whatever reason. Maybe the game treats the two weapons differently, because they do have different skins, and shoot a different looking missile, depending on what team you're on.