Re: Replace outlook!
You forget one other problem: an OS is nothing without applications, and while you cite possible replacements for Office programs, don't forget the existing ecosystem of custom linchpin software that can't be ported...
Yep. Plus, the replacements for Office are often just replacements for basic Word and Excel stuff. Custom add-ins to link into your document management system make moving a bit trickier. Outlook has been mentioned, but Access is also a huge issue that is not typically addressed. There's a lot of database front-ends written in Access, even if the back-end is SQL of some flavour. Often very non-trivial to replace.
