For me it's been just about three years on the Windows Installer team. As other Microsoft-ies will tell you, after three years on a team, it's common to take stock and look around. After some reflection, it's time for a change.
The Windows Installer team has been great. The technology itself is tough to own. Being the Windows Installer PM, thus the face of Windows Installer, is tougher by yet another order of magnitude.
If you've read the book Moneyball by Michael Lewis, perhaps you remember the multiple stories around the "curse of talent". As with baseball, experts can look at Windows Installer, appreciate it's many talents and dream of what it could be.
As Monday is the Martin Luther King, Jr. holiday in the US, his sermon titled "Unfulfilled Dreams" is an appropriate read.
C’est la vie.