I think it is a really difficult one, because you don't quite know how things are going to be during labour (for either of you). For my first birth it was fabulous having dh there, because he fought my corner when the hospital was trying to say I should be induced for fetal distress (meconium stained waters) and all I wanted to do was go home (we were planning on a home birth). dh is convinced that if he hadn't made such a fuss and threatened to take me home they would never have done the final scan that showed ds was transverse oblique (I then had a c-section pretty much immediately). So he had a real role to play, and I really felt supported. It was great to have him there, and I wouldn't have wanted anyone else.
However, by the time dd was born our relationship was pretty iffy and having dh there was not good, and made things much worse between us. I ended up with a syntocin induction followed by an emergency c-section. I think that dh felt like a spare part, he said that I didn't seem to want him in the early stages (my reaction when in pain is generally to shut down) and that when it all started to go wrong I didn't turn to him - in fact a year later he told me he felt like walking out. The difference looking back is that all I really remember is the fantastic moment when the needle went in and the pain went, whereas he remembers all the trauma. Now I do think if we had had a midwife who had been doing her job that would have helped (I can't remember her doing a single supportive thing throughout). But how could we have told it was going to be such a bad experience? All births are such an unknown. My sister had a bad first birthing experience, and I think quite seriously thought about leaving her husband as a result (she felt he backed the hospital rather than supporting her). Second time around she had a doula at home, and a great experience which both her and her dh enjoyed. I just think that it is the support from someone who knows what they are doing, and what both father and mother to be might want and need that matters. I would have been devastated if dh had said he didn't want to be there (which he did say first time around - later said he had decided to be there in case I died!), and I certainly would not have wanted my mother, but more support for me would have made a huge difference.