I finally understand the major reason MS is so hard to displace.   And it has to do with typically American, idiotic busines-by-the-spread-sheet.

We're getting our major business system replaced ... by a .NET system.  I recommended otherwise, the entire tech staff recommended otherwise.  Two sets of high priced consultants recommended otherwise.  But the venture capitalists at the top of the food chain said "dot net".

Discussed it with our divisional CEO, and he finally got it through to me.   Those venture capitalists make no bones about their intention to buy several companies in the same industry, meld them together and sell off the result.  It seems that an MS solution is valued *because* it is so expensive (and otherwise an accepted business practice).  So when the time comes to sell off, the capitalized value of the infrastructure will mean a lot in a service industry with little else in the way of capital assets.

Insane? Yep, but I don't make the rules.  I know just enough about accounting to see how this can work in practice.  Our CEO and his bosses understand that a LAMP (or java) solution would be technically superior, and more stable ... but it wouldn't be as "valuable" (literally) on the books.