My daughter is two weeks old today. In the past 14 days, my wife has been responsible for providing 100% of what our baby consumes, but at least half the time, I'm the one feeding her (we're about 50/50 breastfed/pumped breastmilk in a bottle).
Aside from that, there's effectively no difference in our roles in caring for her. We both change diapers, we both bathe her, we both hold her and comfort her when she's fussy. We don't pay any particular attention to making it a 50/50 split for these activities, but it probably works out to approximately that, for all intents and purposes.
Right now her schedule seems fairly nocturnal (she seems most awake from ~2300 to ~0400), and I tend to be the one up with her during that time, since I find I'm pretty productive during those hours anyway (I've gotten pretty good at one-handed typing).
On a practical level, there's effectively no difference in the amount of care provided between her mother and I. Your statement that her impact is "much more important" is fairly offensive to me (and while I haven't bothered talking to my wife about a comment on Hacker News... I suspect she would be equally offended).