a little followup..
Please, do not even try to say that FileDirectory and FileSystem is interchangeable :)
Colin laid a foundation in a place where was no foundation at all. Yes, in Pharo we did some changes in order to 'make it work', polishing some rough corners, as well as writing tests and documenting the code.
Without laying foundation, nobody starts to build houses.. (well, some do.. but they do not stay long). We even teach kids about that: http://en.wikipedia.org/wiki/Three_Little_Pigs