ultra-wide angles can make easier to spin and butter, but it also makes it harder to do a bunch of things, like carve effectively or do short controlled turns. If you're knees don't feel strained, then there isn't much of a problem.
use what feels comfortable for your own style of riding, but it is also a good idea to play around and try a variety of stances as well too.
One of the best riders i ever knew would just throw his bindings on wherever they looked right, he didn't mess around with measuring the width or angles.
King Shit of Turdville