When looking at technologies like .NET my constant whine is that they are not cross platform unlike J2EE (I don't really consider Mono to be a full plug in replacement). i.e. .NET only runs on Windows. There are other examples of course.
However the problem runs both ways -- many tools (e.g. svn, git, GNUCash, etc) do not run as well on OS/X or Windows as they do on Linux.
For a wandering minstrel such as myself , this makes the choice of personal tools for accounting, development, etc. a curious set of compromises.
Or usually, to hell with compromise and just pick the one that looks cool on Linux (and of course Linus is the father of Linux)