RegClean and RegMaid

Microsoft RegClean analyzed Windows Registry keys that are stored in a common location HKEY_CLASSES_ROOT in the Windows Registry. It found keys that contained erroneous values, and after recording those entries in an UNDO.REG file, it removed them from the Windows Registry. RegClean was last updated to version 4.1 several years back. It is now obsolete, no longer used as it is not compatible with many products including Office 2007 onwards. But Microsoft has nevertheless just updated KB299958 to list the problems you may face if you were ever to use (why would anyone use it now!?) RegClean Utility with these products installed. RegMaid was another utility that was designed to clean up invalid registry entries that were caused by deleting OLE projects that were created with Visual C++ and Microsoft Foundation Classes (MFC). RegMaid was thus not meant to be used as an end-user cleaner, but more for programmers machines. Windows 9x and Windows NT officially support this utility. It too has been discontinued. …And then there was OneCare, which included a  registry cleaner to help remove invalid or obsolete registry items on your Windows computer. But this too has been discontinued by Microsoft. Has anyone here used RegClean, RegMaid in the earlier days? Like to share something about them?