How would you feel if a fellow developer left in the circumstances described?

  Jealous. I would want to leave too and would be pissed that I hadn't found a new job yet.

If you were a dev manager or hired this developer, how would you feel about them leaving in the circumstances described?

  Incompetent. I've already lost this developer due to lack of management skills. Seeing them leave in these circumstances would just underline that good people quit bad managers. I'd be scared that I'd get fired next.