Well, I hate to say it, but he's pretty spot on about his worries and I was exactly the same before DD was born.
Let's be honest about this, the simple truth is that having a new baby is hard work, both physically and emotionally. And (contrary to cosima) both the mum and dad absolutely should be doing it together, so, yes, if your DH is the decent guy you make him sound like, then he will right in the middle of that sleep deprived screamathon with you. You also have to work harder on your relationship as a couple than probably at any other time beforehand.
I'm yet to meet another guy who says "Boy, were those first few months fun or what?" I have, however, met plenty of guys who say things like "They do sleep through at some point though, right?" or "Sex does happen again, doesn't it?" or even "Turns out they show Argentinian football on Channel 5 at 3.00am".
But three key things. Firstly, as CapricaSix says, if you go into it with your eyes open you'll probably be pleasantly surprised that it's not quite that bad as you fear beforehand. I remember before DD was born thinking "I can't wait til DD is born, but it's a shame that I'll never go out/ sleep/ see friends again and my life is now over". It's amazing how quickly your life adapts to fit the new arrival, for example, watching the football with the baby sleeping on your chest instead of a Stella or seeing friends for dinner at theirs, rather than a restaurant. So yes, it is hard, but not as scarily hard as it probably feels right now. Secondly, you have this utterly wonderful and amazing new person in your life which you and he will love like you've never loved anything before, and just as you're about to have them air-freighted to Brazil in the middle of a three hour screamathon, you'll look at them, and just want to fall to pieces with love for them. Everything else suddenly seems trivial in comparison. Thirdly, you are a family. Beforehand really you're just a couple. You might be married, living together etc. but basically you're just a boy and girl going out together. But when you have a child together, you really are a family and you become a parent and you all look at each other, and love each other, in a whole new way.
Hope this helps - if he's really hassled though, just ask him to come onto here and ask the guys on here outright!