One aspect of graduate school at Berkeley I recall quite clearly was the lack of children. Graduate students having children was and is generally quite rare, and I'm not sure that CS at Berkeley was much worse in that regard than anywhere else -- I'd be interested if readers have any pointers to stats on the issue, by field and/or by school. But it struck me even then that it seemed unusual for the faculty to have kids, particularly in the theory group.
I know there's the old advice -- still apparently prevalent in some circles -- not to have children until you get tenure. Though that advice seems less widespread these days, or perhaps just more young faculty are choosing to ignore it. (Or, perhaps, I'm just out of touch -- at Harvard, at least, the common case is for CS junior faculty to have kids.) [And apparently I may also be suffering sex bias; see this summary and this pointer to an NSF report, suggesting that the effect on tenure chances for men having children is small, but is much larger for women.]
Does having kids help or hurt one's work? I don't think there's a clear answer, that it probably depends on the individual (and that the effect, in any case, is probably overestimated). On the other hand, I think a career framework that pushes people to postpone or not have children is ultimately cutting off a substantial supply of raw talent, which can't be a good thing. If academia as a whole is moving away from that 20th (19th?) century mindset, I'm all in favor of it.
(An aside -- Chloe Elizabeth Mitzenmacher arrived last week, prompting some of these thoughts. Which, due to lack of sleep, might be even less coherent than average...)