In all my years of working with text editors, I don't think I've ever found myself thinking "This viewport is too small. I wish I could quickly resize it to just the width of the text, and maybe the height of the screen, or maybe something else, depending on what I'm doing." When my window is too narrow or whatever, I usually just (a) maximize it (which you can't to on osx), (b) dock it to half the screen (windows+left or windows+right on Win7+/*buntu, but not on osx) or (c) just quickly drag it over. So Apple effectively forced us to use only option (c), which is probably the least useful of the three sane options. The only other option is to use a feature that doesn't really do what we (or I, anyhow) want.