You usually only hear the catastrophic failure anecdotes. Large, complex, yet successful rewrites I know about: * The Windows kernel. From my understanding, Wi

You usually only hear the catastrophic failure anecdotes. Large, complex, yet successful rewrites I know about: * The Windows kernel. From my understanding, Windows NT was a completely different kernel from Windows 95 and eventually replaced it in Windows XP. * Coldfusion, I used to work with an ex-Adobe guy that told us the story how this was rewritten from scratch at one point. From C++ to Java * I used to work on the SQL Server team at Microsoft. We completely rewrote the Reporting Services product between the 2005 and 2008 releases.