My husband did some research and reported to me that he didn't want to see the business end of things, because there's a much higher divorce rate for couples when the man sees his 'holy grail' as a trauma site. (I have no link to back him up. No idea where he gets his information.) His plan was to stay 'topside' and support me/be with me while the midwives handled the rest of it.
He changed his mind in the birthing room, said it was really cool, and was glad to be involved in that part of the process too. I personally can't imagine NOT having my husband with me during birth.
On the other hand I know a few progressive men who were excited to be involved in and present for the birth, but felt pressured to catch or cut the cord when they weren't interested in that. It lessened their enjoyment of a special moment with their wives/girlfriends. The assumption that birth friendly = cool with gore is not to be made lightly.
I had a vacuum assisted birth after several hours of pushing (otherwise invtervention/drug free), and ended up with a third degree tear. 45 minutes of stitching later we were finally able to start nursing. I can tell you that he was horrified FOR me, having nothing to compare the idea of that wound to, but certainly not horrified OF me! My tear healed nicely, we struggled to wait 6 weeks before engaging in intercourse again, and he doesn't at all find me less appealing. If anything he is in greater awe of my body, and practically worships it.
We prepared ourselves with humor before hand, recycling a joke a friend made about her husband "Slipping the doctor $100 to stitch her up tighter than before." Sorry if that's too much, it's crass I know... but we found it funny, and it was a good way for us to deal with the strange ideas women and men are given about the after effects of birth. I've actually heard someone say "Enjoy it now, because your body won't be the same once you have kids." I think it's terrible to set women up with a bad body image about the 'damage' they're doing to their body before it happens. Change DOES NOT = Damage! Some women feel more secure in their sexuality after giving birth! And if you don't, that's ok too. There's a lot going on in and around your body at that time.
As for your partner's view of things, he may or may not be comfortable with seeing something that awesome (remember that awesome includes staggering in its definition), it may take some work for him/you to decide together what to expect. Men are subject to just as much speculation and myth of what a 'train wreck' their partners bodies will become after birthing children, whether they see that happen firsthand or not. It may be demystifying for him to witness it, or as my husband's statistical anecdote shows it may be too much. I think it's important to talk about before hand, but just as important to be realistic about his squeamishness level, visual memory, etc...