Excellent question, db. I have a little bit of strap-on experience. I have one with a short dildo that goes in me, and a longer, narrower one for my recipient. It's delightful, but I've never managed to have an orgasm with it. In fact, it's arguably a bit distracting. Especially while you're both still getting used to it, it's best for both partners to concentrate on the one who's receiving anal--he's the one who should set the pace. (And use lots of lube!)

Anyway, it doesn't make me cum, but it does make the experience a little more stimulating for me. The best part by far is seeing my partner bent over and vulnerable.

It's also fun to make him lick, kiss, suck, and stroke my fake cock. Obviously it gives me no direct stimulation, but it's fun to watch!

I've never witnessed a guy having an anal-only orgasm, but the anal stimulation can make for a totally explosive orgasm.

If you've never had anything up your ass, I highly recommend you pick up some anal beads and try them out when you have a night alone. No partner required. They're easy to use, conducive to subbie fantasies, and they feel amazing!