I think absolutely the most important point made in this thread is this one - that everyone is different. Everyone reacts differently to different stresses.
Some people can deal with less sleep, others really can't and so the early weeks become hell on wheels.
Some people can cope with the noise of baby crying, others really can't.
The point I'm trying to make is that it is utterly unreasonable for any poster to say "well I managed this so therefore it's going to be ok for you too" - you cannot POSSIBLY know that, because You Are NOT Them. They Are NOT You. Their sensitivities, their flaws, their lives will be different - and they might struggle with things that you don't (and vice versa, you never know!)
And for some, yes, the bad will outweigh the good, sadly - undiagnosed PND could be a reason, or they might just be missing the maternal bone, or they might have been coerced into having the child(ren) in the first place and really resent it.
But for most of us, the good will outweigh the bad. Most, not all.
For you, OP - take the positive, and try to forget the strongly negative - you have the choice what you take away from these threads. :) 