I have been using Emacs heavily since the mid-1980's on various platforms, and I still hack elisp extensively. Because everything I would run in X11 these days has been ported to native Cocoa versions I no longer run X11 on my Mac. I've tried other Emacs ports but I always come back to this one, and have been using it and its predecessors for years. It is an excellent port that is true to standard Emacs. It does not insist on intrusive UI interfaces or limitations, but it does provide UI conveniences if you want them. It behaves well as an OS X application. It includes a well thought out selection of libraries in its site-lisp. It is fast and completely stable. It's got some extra libraries to do Mac things -- even execute AppleScript code. I greatly appreciate the work that has gone into fitting this port into OS X and continuing to improve it.