Wasted experience, when Microsoft decides to totally change their dev chain/libs for business/marketing reasons. VB, .net, activeX. Last 20 years of MS dev is littered with them.
Wasted time upgrading / relearning OS because MS has end of lifed it and requires new OS for tools to run.
Wasted opportunity when you discover there is market outside win32 but it's too expensive to target cause all your products/libs/experience is invested into a proprietary stack. Vendor lock in is expensive in other ways as well.
Inability to find/fix bugs in stack cause it is closed source.
Inability to tune/add feature/etc stack cause it is closed source.
Those are some of the first that come to mind. There have been essays, articles, papers, and blogs galore written about how and why closed, proprietary < open / standards compliant. I'm sort of stunned anyone reading HN needs to schooled in that.
