Never ever actually use it for vibrato I've always just used my fingers. I don't think I've written a single bit of lead that uses a trem for accenting and vibrato, only ever for huge dives
I've started playing around with it today though and it's certainly a different flavour, has a bit more of a 'moody' vibe to it. I'm going to have to start using it like this more often.
Flutters are awesome as well. Can be very subtle, but used in the right place can give certain notes in a solo a whole new life.