A pleasant form of over engineering, vim is a rather odd but ultimately useful text editor. If you use text editors to do a lot of work (eg you are a writer or programmer) then vim is a tool worth mastering. The advantages of vim over an ordinary text editor is that it is as concerned for editing as it is for typing, and all without moving your hand from the touch typing position.
So editing is performed by keys or chords of keys. A key press in normal mode does something like move the cursor or search for the current word, jump to a previously marked position etc. This doesn't sound as impressive as it is. Because people do the same dam thing in a text editor a lot, for example jump to a previous spelling mistake and look at options, these series of key presses become lodged in muscle memory like walking or changing gears while driving. You just do it, so movement keys become more like an alternative language, but only after a bit of use. Until then, it is more of an intellectual curiosity.
While there is a lot to learn, you will make up the time from efficiency, but more importantly, when you are doing something otherwise dull, you will get distracted to learn how to do something obscure, but useful rather than manually changing a lot of indentation. This leads to a sense that you're actually present infront of your computer rather than simply zoning out. So a major argument is really that it is just a nicer user experience in the long run. Nothing is repetitive and everything is a puzzle. What constantly surprised me was that there was some obscure setting to speed up a little detail, and that attention to detail was on some level nice for its own sake.
Another advantage is to avoid the mouse hunch where you lean to the forwards to one side. Granted sitting in front of a keyboard does not do wonders for your posture, but if you're editing pages of text/code a day then you do spend a lot of time hunching over and jumping between mouse and keyboard. With vim, you are in the touch typing position and your hands make the minimum of movements. That is not to say you are lazy. When I type it is generally a little frenetic as I try to get the idea out of my head before it disappears, but with vim this equally applies to editing as well so you can perform more subtle edits over a fixed period of time.
There is a nice fluidity in keeping your hands close to where they are about to be useful which avoids irritating little pauses while your hands catch up moving to the appropriate position. This is taken to absurd levels for example when you realize the most irritating thing is that you have to push the escape key (and use instead), then move to the really strange level of using -m for return and -h for backspace. But don't rush these things, their is a constant learning process where you learn the next best time saving step. And your muscle memory for keys will become sufficiently automatic for it to feel natural rather than contrived or forced. Incidentally, and I don't know if this is fatal for future back problems, it offers a realistic way of editing with a laptop on a couch as their is no annoying scrolling with the touch pad, so you get more variety that way too.
So vim is in the long run far faster and intuitive to use. It is more interesting in the ways you waste your time and is ultimately a nicer experience which puts less strain on your hands. A sign that I was 'ready' to move to vim was when I preferred shortcut keys for things like save , find or move a word at a time in notepad. So if you're getting board writing a lot of text, give vim a try, but remember to be very patient for the first few times and play through the tutorial.