i've never been impressed.
i just recorded my drummer's kit with a 57 on the beater and it picked up quite a bit of bottom snare. if i end up using a lot of beater in the mix, i'll probably have to gate it because that brissly toothbrush sound makes the snare wimpy, to me.
i could see it being a good thing for light brush playing or something, but for a thick rock snare i don't think i'll ever like it.