I never would. I'd just assume it was a guy sucking me off. I mean the whole idea of it, what are they hiding?
It's not for me, the visual turn-on of an attractive woman is too important to me.
But, if you're up for that sort of thing, and can get off on it, does it actually matter that it might be a bloke? Isn't the point of it to make it just a physical experience and nothing else?
I'd quite like to be able to not care what's at the other end, but unfortunately I can't.