However, most of the people here are Linux by default on their servers, and whatever comes natively on their laptop - which for most web developers seems to be OSX these days.
To address your points (quickly) :
Incompatibilities : DOCX isn't even compatable between Microsoft products, and we recently noticed that gmail converts it silently to DOC : Making it a broken format if the documents are ever sent over the web to a client.
Interaction : Not as much of a problem as Microsoft would like. Clients seem quite ready to accept formatting snafus as Microsoft's problem. For WYSIWYG, use PDF. For editing, formatting is flexible. Conversion team HA!
Installation : LibreOffice on Linux is a much more scriptable solution that Windows/Office. Purely because of licensing issues. Difficult to take a lecture on security...
Email : Selecting a decent email client is pretty easy. Particularly since Microsoft Outlook's implementation of IMAP is so broken. If you're interested in restriction employees from forwarding emails, I guess that's something that could be handled by some sort of corporate email relay - which will probably run quite nicely on a UNIX system.
Visio, Project, or OneNote : Actually, not everything has to be bought from Microsoft, does it? This is kind of scraping the barrel, unless your solution requires all software to be bought from Microsoft.
I'm pretty certain you'll have plausible-sounding rebuttals to all these points. But (short of downvoting me off the page) my off-the-cuff response will be linked to your copy-paste effort for everyone to see.