Using "vi" in Terminal

I've been trying to use the editor "vi" in Terminal. All I get is a lot of control characters (I'm trying to edit a .plist file). When I did this on my 10.2 and 10.3-running iBook, I got the ASCII file I expect. What am I doing wrong?

(When I create a file in vi, it stays as an ASCII file).

MacBook Mac OS X (10.4.6)