Yes, it looks messed up on mine too.
If it were working properly, though, the white/yellow gradient you have would turn out like this with Multiply:
<img src="http://i42.tinypic.com/v6izk7.png">
So if you're trying to make a vignette effect then I would just make a gradient that goes from transparent at the center to black at the edge and not apply a shader.
But, uh, yeah, that's a bug that needs reporting anyway.