The circumstances, degree of intimacy etc can have a HUGE impact on the whole experience.
But speaking stricktly in terms of sensation, if the woman is aroused, the vagina feels very welcoming. Probably the same temperature or slightly warmer than your dick, very slippery, soft but with some pleasant resistance to stretching. Sliding in and out feels very good, better than masturbation. If you go very deep, depending on your dick size and her depth, you can "bump" into soft walls which may be either her cervix or just the curvature at the end. The walls also don't feel perfectly regular as you see in books, they are slightly more tight in some parts and more lose in others.
If she isn't horny, then it isn't nearly as pleasant.
But again, the whole experience of sex (even talking stricktly about PIV, not even accounting for foreplay) is largely variable according to circumstance, intimacy, the girl's enthusiasm etc. My wife's pussy feels like a good and tight pussy, but she pulling me inside like her life depends on it while moaning close to my ear is what makes it the best experience in the world to me.
Lack of intimacy could turn the same experience into "ok I guess".