As for being the only comment/activity, I've had that happen to me a few times here already!  Someone even signed up with a username about the product I had reviewed (as in "productsucks") and then the only thing they did was leave a comment on my review that I must not know what I'm talking about b/c the product sucks.

I just replied quick and nice to say I do use the product all the time and I do love it regardless of what he says.