The procedure itself was a little...pinchier than I remembered from when I had it in 2006. But it was a lot faster, because I had given the radiologist a heads-up about my unicornuate uterus ahead of time (and since it was the same facility where I had my previous HSG as well as the MRI confirming the UU diagnosis, he was able to call up the records), so he didn't have to waste time trying to get dye to flow through a tube that isn't there. I also haven't had really any cramping, again I think because I didn't have all that extra fluid pumped into my abdomen.
Also, my uterus looks exactly like a tiny banana. That is all.