Great question for a thread. I've always been curious about initial penetration pain. One of the tightest women I've been with was my 2nd ex wife and it was always apparent to me that no matter how hot, bothered and wet she was, the outer surface of her opening was always dry. A small dab of spit would make the biggest difference in the world opening her up the first time. Once my cockhead has an opportunity to enter her, I can usually drag some of her lube back out to the surface.
And there is a big difference in the quality of pain too. I know the OP asked the women, but here's my counterpoint of view: If it isn't wet enough, the pain feels like a rubber band sliding across my cock and it feels like her skin is getting dragged in as I try sliding it in. The sensation feels like I'm about to split some skin if I push any further.
The wet kind of pain has more pleasure mixed in. This is the most confusing for me and unfortunately where the most damage happens. Not necessarily a mixed signal, but more of a hardcoded, "hurts so good" cycle. I like petite's description for her vagina as it feels similar for my cock. The part that becomes a dilemma is when my wife orgasms as a result of the stretching. If I move it adds to the pain and makes the orgasm stronger, but it also shortens the whole experience overall (the more pain from the initial penetration, the more likely we'll have to quit sooner).