Also being available everywhere. I like Text Mate quite a bit, but being single platform makes it harder to recommend.
Emacs is everywhere. Windows. Linux. GUIed. And in a terminal where I've SSHed into a remote host.
TextMate? Nope. Sublime text? Nope. Atom? Nope. LightTable? No chance.
These modern GUI-only editors is IMO a major step back considering the Unix-y audience they are targeting: Any decent Unix-editor needs to work on my console. No exceptions.
Not everyone feels that way. For example, I used Emacs in text mode for over 15 years, but now that I have tried editing text in a GUI, I do not ever want to go back.
Also, network access isn't equivalent to console-accessible for quite a few use cases--fixing networking on the target box for starters.