The rare occasions I've used, or shall I say been required to use a condom for oral has been with some "straight/bi" guy that's paranoid about catching something and bringing it home with him. I totally understand. And while the taste is not pleasant at all, the act of pleasuring this kind of guy is pleasurable to me. Many straight men and female hookers have used condoms for oral way before the AIDS crisis began. There are ways of making it pleasurable for the receiver, like making sure it very wet inside and out and lots of hand and mouth movement.
And as far as STD's, I personally knew somebody who had gotten clamidia TWICE just from receiving blow jobs! So yes, oral sex can be risky. It's all up to what you want to do and what risks you are willing to take. I don't judge anybody when it comes to these things. We all gotta do what we gotta do and these are private and personal choices between the participants. At least now we have more options and information available to us than way back in the early days.