OK, here's the lowdown.
First: It's fun. All the women I've had period sex with tell me that things feel a bit different, maybe more sensitive. They've all really enjoyed it.
Second: There is a bit of mess involved, depending on flow. She's going to want to clean her thighs off afterward, and you're going to want to clean your cock and balls. If it's near the start of her period, you're probably also going to want to put a towel beneath the two of you. Once you get past the fact that it's messy, the blood is really nice as a bit of extra lubrication.
Third: I certainly can't remember any smells that were more unusual than normal.
Fourth: Listen to Jadz.
Well, that's about all I can think of to say. Like you mentioned before, she should be really horny at the time, so I hope you take advantage of it.
