Some of you may remember a while back that Ubuntu made a change to their base system: they replaced the target of /bin/sh with dash, rather than the accustomed bash. This immediately began breaking things (in at least one case, expensive things sold by Borland), and a flamewar ensued, with Ubuntu developers explaining that it should work and that therefore they should not make any effort to reduce the breakage, and users explaining that should was not good enough and they would really rather like to take the minor performance hit and have things not break.
This here article, which I found over at Shamus's blog, explains who's right and who's wrong in this debate, which is currently being rehashed with Internet Explorer 8 (Eight? EIGHT? Wasn't six going to be the Last Version?) and Web Standards.