MS Visual Studio
Microsoft Visual Studio .NET is the IDE from the Windows manufacturer Microsoft. Starting with the .NET versions, support for adding plugins has gone better, although full access to the internals of the IDE require a license through the VSIP (Visual Studio Industry Partner Program).
A DocSynch add-in for Visual Studio .NET 2003 is planned, but there is one main problem regarding the editor windows: hooking for single text/character insert and remove events is not possible with a standard add-in (it only offers line changed events). Real events require the VSIP.