With the recently announced AddOn Studio for World of Warcraft, an open-sources dev tool, developers building World of Warcraft add-ons can get the Visual Studio experience without requiring any version of Visual Studio to be installed or licensed.  The developer environment makes use of the new free Visual Studio 2008 shell.

Included in the VS2008 Shell, is the XML Editor and XSLT Debugger which earn high praises from WoW developers on http://www.wowwiki.com/HOWTO:_Set_up_Visual_Studio_for_WoW_XML