This is a big overlooked weakness of both Emacs and Vi(m). After about five years of using Vi I switched to a friendlier editor, NEdit; within a couple months, I was better at using NEdit than I was at Vi, mainly because of discoverability. I then used (X)Emacs for a couple of years (mainly for Python programming, though the original motivation was learning Lisp), and found it rather opaque. Now I use TextMate, and I've had the same basic experience as with NEdit.
Also Textmate / eText / gedit with gedit plugins have:
* Richer interfaces (eg, code folding on out of the box)
* Better discoverability (eg, you can stumble upon how to change your tab width faster in these apps than you can using vimtutor)
* Easier customization (ever tried writing a vi syntax schema)?