It is fun because it is fluent. vi has a language.

If I spend more than a couple minutes in an arrow-keys-and-mouse text editor, I often find myself unconsciously reverting to vi-language and getting confused. "Oh, I want to go change that sentence up the page that starts with 'Looking at...'" so I type "?Looking at" into the text editor and then stare at it for a few seconds before hitting backspace and reaching for the mouse like a caveman.

I like to think of it more like a bytecode.