You know, Imp, I'd be in the same place. I don't have anyone from my past who I wish I had done things differently with. I have one friend who I'd love to have a fling with, but I know he'd never make husband material for me - and he's married now, so that's a door closed.
Still, I think it's romantic and fun when people who do have those possibilities connect again. A faculty friend of my dad's reconnected with and married a woman who was an ex-student (and had been a favorite babysitter for me and my sibs), and they are really happy now.