I think you always want to be a little more cautious after two people decide to start dating fresh out of a relationship. Really ask yourselves WHY you're dating to make sure you're getting together for the right reasons. As long as you feel comfortable with the WHY, the rest should be okay.
A lot of people are hesitant about dating right out of a relationship because it can sometimes just be a distraction from the pain you feel about the previous relationship. It sounds like his break up was one more of convenience than because they don't WANT to be together so I'd be careful that the emotions in his relationship are really over.
Likewise, your relationship ended and it sounds like you're a little hurt that it ended exactly on the 10 month mark. Are you over that? Are you ready to move on?
I don't think there's anything wrong with dating an ex as long as you're doing it for the right reasons and you're sure you're going to get more out of the relationship than you got the last time you dated. Good Luck
