I was trying to make Windows a little more Emacs-friendly (or was it the other way around?). First step was to enable the emacs server in my .emacs so I could make use of Emacs for quick and dirty editing tasks that require an editor better than Notepad but where the average Emacs startup time was just a little too long to make Emacs a viable alternative. A typical example would be to use Emacs as the editor for commit messages in Mercurial. A quick tweak of my global .hgrc provided me with an appropriate editor setting:
Please note that there are no quotation marks around the emacsclientw command line, adding them will result in an error message rather than an Emacs frame. Guess how I found that out. I would also suggest to extend the command line to include the "alternate editor" parameter -a to either start Emacs or another editor if there is no Emacs server running. Given that I tend to start Emacs right after I start the browser and the email client on most machines, this would be an unnecessarily cluttered command line for my use.
I also set up Emacs as an external editor from Visual Studio as described in this blog post, so now I can hit Tools/Edit in Emacs from Visual Studio 2012. Hooray! The only tweak I made to the emacsclientw invocation described in the blog post was to make "+$(CurLine)" the first parameter of the emacsclient invocation. That way, the Emacs cursor position is synchronised with the cursor position in Visual Studio at the time you invoked "Edit in Emacs".