Minnesota is considering changing its custody laws to presume that parents will share physical custody. That does not require shared custody; but it establishes that as the presumption, unless negotiations or a judge's ruling lead elsewhere. Only a handful of states--notably Iowa--have moved in this direction. Fathers' advocates generally like it, believing that it gives them more rights following divorce. Women's advocates are generally unhappy about it, for the same reason. And experts are divided.
And a study out of England suggests that good fathering has benefits. Here's the gist of it, from New Scientist:
"The more effort a father invests in his children, the smarter they are as kids and more successful as adults, new research shows. And highly educated fathers make even more of a difference than less educated dads, all things being equal."