I just learned about Zile, which is a mini-Emacs. It has most of the editing functionality (including multiple buffers) and works great as an editor to install on servers when you don't want to put full GNU Emacs on there.
I'm still not sure what is missing, but basically I think nearly everything is missing except basic file editing. For example, not Text editing modes (e.g., HTML, Python) are not there.
Also, a key combination I use frequently to scroll down a page I'm reading, C-u C-v, which by default scrolls down four lines, in Zile will page down four times. As a slight consolation, C-l will still center the line the cursor is on.
Still, for me as a 22-year Emacs user, this makes a perfect replacement for vi when you need to edit /etc/hosts or quick, little file edits like that.