I'd honestly ask yourself whether you're willing to walk away from an offer if what the guy says is bad.  If you are than talk with the guy.  If not than I wouldn't.<p>Because he's going to be bitter.  So you're going to learn a lot of bad stuff about the place you're starting at.  That's a disadvantage in itself (because you might develop his prejudices and run his old enemies the wrong way).<p>So if you aren't prepared to walk away than you're just torturing yourself with the information and making yourself less effective at a time when you need to be at your best (a.k.a. the beginning of your new job)