The article http://www.pff.org/issues-pubs/pops/pop7.4microsoftmonopolyf... gives irrefutable facts. Do not accuse me of rewriting the history. I was there to see the birth and death of many good products that have been killed by Microsoft tactics (dr dos, stacker, framemaker, borland C++, ...). One of my most usefull book at that time was http://www.amazon.com/Undocumented-Windows-Programmers-Micro.... Many people have lost a lot of time because of the monopoly of Microsoft. How much time lost because of IE6 ? I have lost a lot of time between 1999 and 2002 because visual C++ was not compliant at all with the standard published in 98.
My opinion is that all the time lost because of Microsoft has been detrimental to computer science progress.
Undocumented API calls were rumored to be a big deal even back in the Windows 3.x days. I remember reading through this at the time looking for the 'smoking gun'.
https://www.amazon.com/Undocumented-Windows-Programmers-Micr...
There were some cute and offensive names, and a few interesting details about the internal implementation of Windows, but nothing that would've been hugely beneficial.
Things might well have changed since then. (Both at Microsoft and at Apple, where their software is definitely allowed to do things that third party software is not.)