My mom had 7 NCBs and Dad missed only one (didn't make it in time) -- she and he both regret it. Even though Dad almost fainted during Mom's first labor (the doctor had to catch him). This was when they first started allowing men in delivery rooms (early 70's).
I think a lot has to depend on the spousal relationship, as others have said. Dad is a pretty patriarchal guy in a lot of ways (his father figure was his grandpa) -- but in terms of birth/babies, Mom is the expert and Dad pretty much backs her up. And while there are things that bug me about their relationship -- it's a lot more egalitarian than some of the other marriages I've seen in their generation (and far healthier communication).
DH and I have only had one birth together (one more coming soon)
) -- he was great. He worried a little about what the OB etc. would think of his approach (he tends to joke about things) -- I told him not to worry and just be there for me, and he was. Very calm and absorbed and focused (and yes, funny
) - I know he was nervous (he's more scared about birth than I am, and way less NCB background than I have via my family's stories) -- but I don't think it slowed me down at all. He did a good job of deferring to me and allowing me to do what I needed to do. Much as I really like our OB, I would have had a much more difficult time if dh weren't there. Of course, I'd like my Mom there too but she really feels that birth is between the mom, the dad, and the attendants. I think the only way she'd accompany one of our births would be if the daughter in questions's dh was unable to be there for some reason.
In terms of bodily functions - I can totally see that being an issue for some couples. Which is sad, IMO. A friend of mine told me his dad told him that you know if someone is "the one" once you are able to go to the bathroom in front of them (or they in front of you) and are still comfortable.
I've got a good friend who doesn't want her dh in the room with her when she's in labor because she doesn't want him to see her "that way."
I don't think he'd want to be there anyway. I think there's a difference between recognizing that there might be negative energy due to a dh's nerves etc., and wanting to maintain some mystique about one's body to the extent that you don't want your partner there (and I think that the mystique is being maintained FOR him, not necessarily for her, KWIM?).