I'm one of those people who quite likes playing mediocre characters. Making the best of a bad lot is fun, especially if there's a humourous angle. But I also tend towards the view that there is something virtuous in overcoming the trials and difficulties of life as a bad character.
RPGers don't really talk about practice - not these days, anyway. I believe Gary Gygax may have mentioned it somewhere. But anything worth spending time doing, whether learning the saxophone, playing rugby or practicing keyhole surgery, requires it. Why should role playing be any different? And in the same way that playing chopsticks over and over again on the piano won't turn you into Rachmaninoff, surely playing uber-munchkin characters won't help you get very much better at your game of choice, either.
This is the problem with min-maxing and why it was always considered anathema, I think. Bring on the mediocre characters and the protestant work ethic for role playing!