Well personally, when I'm on my period, I like to get a bit of scissor action going with my ovulating girlfriend; I mean the sex is great, don't get me wrong, but cleaning up that sloshy bloodbath is somewhat of an ordeal.
Why not? We just put a dark colored towel down and wash off after. :P Not big on the shower sex thing, my boyfriend is really tall and I'm really not, hard to get a good angle XD
Fiance and I just do it in the shower so we can wash off after or use a condom to minimize mess. But as I am on birth control my periods are fairly light.
I had it for the first time a couple of months ago and I had no idea how much I was missing out.... Might not be for everyone (Not for me every month, either), but it's definitely worth trying at least once