Yeah, when I was using the weaker or lower-dosed opiates in the early days, they got me horny as fuck, funnily enough; when my use escalated to heavy levels though, I became "skaggy bawled" in the words of Irvine Welsh: I had no sex drive whatsoever, and sex played no part in my life. (And who needs sex when you've got heroin...?)
I'm on bupe now, and it hasn't affected my libido at all, but it's given me a definite loss of sensitivity in the place it counts - the sex just doesn't feel as good anymore, although I last a lot longer. If I'm with a partner who doesn't completely arouse me, the sex becomes a chore tbh, and it's led to a loss of erection on more than one occasion, which is fucking embarrassing.