Here in WI, there's no waiting period--but after you file, the divorce must wait at least 4 months.
My ex and I (no kids) filed pretty much the week we realized there was no going back. Once you're sure, here, there's no reason to wait.
ProtoLawyer (the now-actual lawyer, this isn't legal advice, please don't take legal advice from some anonymous yahoo on the Internet)
Spouse (the political geek) * Stepdaughter (the artist) * and introducing...the Baby (um, he's a baby? He likes shiny things).