If you design for the 1%, (long live LYNX!), then it works for the other 99%.
If you design for the 90% IE users, you piss off the extremely vocal Linux (and BSD!) users running Mozilla. And some of the Mac crowd because they love to complain too. Then the Netscape users will speak up because they might as well at that point.
So it depends on how flame-resistant you are, if you're willing to alienate the zealots by telling them to take their non-conforming OSes elsewhere, and if you're willing to lose that diversity.