So, MS products are based on not only MS/clean-room ideas, but also the best ideas taken from their competitors.
In otherwords, MS is borg-like.
Nonsense. This happens in every industry. Do you really think all car manufacturers indepentantly thought up the idea of in-car radios or electric windows or whatever? Did TV manufacturers just happen to all think of remote control and On-Screen displays at the same time?
If a competitor has an advantage that you can be "inspired" by, then it'll end up in your product. Maybe with your own spin on things and hopefully improved a bit.
It's also bi-directional. Apple's Dock clearly lifts ideas from the Windows Taskbar (wheras the Start menu is an obvious clone of the Apple menu). Almost every Linux gui borrows heavily from Windows (with the odd bit of Apple here and there). Nothing is 100% clean room and neither could it be, unless you locked your developers in a dark room and never allowed them to see the real world.