I keep my code portable to Windows soley for the purpose of getting to use the Visual Studio debugger. Likewise, Windows developers should write portable code so they can use valgrind.
"Often time when using high level algebraic languages we have a tendency to do things in a way that looks the best, or in the shortest number of statements. Often completely ignoring what will execute fastest." - Donald Knuth The Art Of Programming Volume 1 Second Edition Preface X.