I used to think like that, then I realized, I am going to be editing text for at least the next 20-30 years (if not longer). I get the feeling vi(m) (and emacs) will be around then, so it's an investment worth making.

It only took a few weeks to reach the efficiency I had with TextMate, and every week since I've become more and more efficient. I haven't hit the point of diminishing returns in learning about my editor, and judging by other vim users I've seen, I probably won't for a long, long time.