I generally agree, I want the full git interface, which is available everywhere and has no limitations and is not bound to a particular editor.

There is however one area I do find useful to have integrated into an editor, various kinds of code annotations... e.g gitgutter, I use this in vim - these type of features compliment git porcelain rather than replace it. i.e gitgutter is no git diff, but it gives you a good feel for what's been changed before you jump into staging. I've never used magit, I wonder if it has such features? or is it really only a git porcelain shortcut?