I guess I gotta be honest here. I ask my fiance that all the time. Usually if I"m in a joking around type mood or we're watching TV and they're talking about that on the show or something. Sometimes it works, sometimes it doesn't. I would have no problem with my fiance asking me that. I'd probably make a joke out of it.

We've had problems with the flirting/subtle hints before in the past. We still do that, but they don't work 100% of the time and can lead to hurt feelings, etc. When you ask straight out, there's no confusion. And, my fiance's favorite thing to say about anything sex related? Variety is the spice of life! So why not mix it up a little every so often?