Re: POSIX
Windows is not a fully OO environment - most of the Win32 API is a C one (some more recent ones uses interfaces and C++ semantic, others may use COM, but still is not a full OO API especially since there's no inheritance).
That said, Windows implements a different model than Unix. Sometimes it's better, sometimes it's worse, often it's just different. Using SUA (an optional component) you can have a POSIX environment on Window, but IMHO, any first class application in Windows has to work as a "native" one, not pretending to be still in its *nix environment, and should not require any optional compatibility layer.