If you are interested in Unix and all its flavors, learn vi.
No matter what box you land on, I guarantee it will be there. Emacs probably won't. Don't get me started on LaTeX.
Trust me on this one, I get paid to know this stuff.
Let me second that...if you want to work on commercial unixes, you must learn at least a bit of (the commercial vendors' typically minimalistic) vi. (as compared to vim)
Oh - and IMHO, that one-liner jobie "ed"... blows.