There is an infamous library called dispatch. Someone put together http://www.flotsam.nl/dispatch-periodic-table.html to try and help other developers out when using it. I use it because it is good... but hell. The lack of discipline there is awful.

The problem is that, out in the wild, you're going to end up with legacy code made by people who picked a different sub-set.

This is the situation I've been in for the last year and I agree that for every point I make in praise of language flexibility this is the strongest counter-point.