Let us not forget Irving Berlin, and his sliding action Steinway (is it still on display opposite Carnegie Hall at the Steinway showroom?). Here's a guy that wrote some of the best tunes ever, and he could only play well in the one key...
The trick is to mitigate your weaknesses, not display them proudly and say 'I could use a transposer and sound MUCH better, but I choose not to, because I am a REAL musician!'.
BTW, Russ, what do you do when the singer IS the bandleader, and wants to do things in strange keys (and you are subbing for the night)...?
Me, I do what it takes...