I didn't exactly take a paternity leave. I'm a college professor and my son, Nick, was born three days after my last final exam of the Spring semester. Perfect timing (although we didn't actually plan it that way). I was able to spend the summer on a "de-facto paternity leave" with my wife, Amy, and Nick as we all got to learn how this whole "baby makes three" thing would shake out.
For me, bonding with Nick was immediate. Amy had to have an emergency C-section, so while she was in recovery, the first hour of Nick's life were just me and him. I spent that hour touching his little fingers and toes and vowing to him I would do all I could to be sure he would have a happy life.