So I have just discovered something, and I wanted to confirm this with the setup gurus (or alternatively they could tell me if I'm talking through my... output jack).
I recently did a replacement of the pickups on my axe, and at the same time changed the saddles on the bridge, from the standard solid-block-type ones to some Mitey Mights (?) which I can only describe as arched. Below are the saddles in question:
Before
After
Now I never use my whammy bar, for two reasons. Firstly, I don't play any particular songs that really require it. The second, and main, reason is that I could use it maybe twice (very lightly) before my guitar was horribly out of tune.
Now, for the first time in possibly three years, I decided to try getting into the whammy bar thing, just to try something new. Slowly but surely it got to the point that I was doing some violent "divebombing" and generally throwing that whammy around. And my tuning was absolutely rock solid... Does this have anything to do with the saddles? The contact areas of the strings over the saddles is understandably quite different, could this have saved my vibrato?