I have used it to great effect in-game.
You are correct though, if done at the wrong moment or in the wrong situtaion, you might as well just bail out and save yourself a death.
The closure rates are important. If they are just creeping up on your 6, it will result in a swift death. If the closure rate is decent, but not too high you will find yourself with a kill-shot or at least an escape.
In the case of a P-38, they won't roll with you, especially not at slow speed and if even if they do get a shot off, a P-38 snap-shot rarely results in death. (at least in my experience, that is)
As a side note, the engine-deterioration effects after the 109 gets ganged are very, very cool. Wishlist material for sure.