Some thoughts:
FrankS' original premise was also what I found in my personal experience. I began photography by "chasing the needle." I eventually learned to hunt for and find neutral gray in the scene. Shooting slides, I started using a handheld meter and felt I was really beginning to understand light and how to meter it. Just as important is to understand that there often isn't one exact exposure for a scene but trade-offs that give you varing results and moods. I'm now comfortable with any metering method -- in camera, out of camera, incident, reflected, no meter at all -- because the meter had become just one more tool.
Truth be told, I have hardly ever used a meter for the past 10 years and don't currently own one that I consider to be pocketable enough to carry around. So I fully agree with the observation that a meter is one of those things where, once you learn how to use it, you don't need it.
I wouldn't knock 18-percent gray cards. If they shout "photo-school student" then so be it. There's a lot to be said for going through that step in your learning process if you really want to become technically proficient. If you're worried about appearance, you should still feel free to use the card in the privacy of your own home, at least until you reach that gestalt moment where you understand why a picture of a black wall and white wall will meter into the same neutral-gray picture if your in-camera meter is left to its own devices. In photojournalism I used to also run into the "how do you meter for black people?" question. Once you know the answer to that, toss the gray card (or slip it into a little-used pocket of your camera bag).
And don't forget the old rule of thumb -- with negatives, expose for the shadows, with slides, expose for the highlights.