For a nuanced look at the complex emotions of parenting, I highly recommend Jennifer Senior's book "All Joy and No Fun" (http://www.amazon.com/All-Joy-No-Fun-Parenthood/dp/006207224...). There's a condensed version here: http://nymag.com/news/features/67024/
All Joy and No Fun: The Paradox of Modern Parenthood discusses this (https://www.amazon.com/All-Joy-No-Fun-Parenthood/dp/00620722...), among many other interesting topics.
I'd also observe that there are probably time-sensitive issues; much of the day-to-day stuff with small children is dreary, but the long-term prospects are quite good. I've heard lots of older people say that having adult children is great, because they're self-sustaining and yet emotionally close / connected.
Many long-term projects (probably including startups) have somewhat crappy day-to-day moments but high long-term satisfaction. And many short-term satisfactions (like eating ice cream) may have negative long-term consequences.
Bryan Caplan's book Selfish Reasons to Have More Kids: Why Being a Great Parent is Less Work and More Fun Than You Think is also good on these topics, and he points out that much of the supposed happiness research is overblown or misused.