Agreed, and I do Drupal development from time to time. Restricting common browsers like IE, Chrome, and Safari entirely is a great way to tell people to go away.

Simply popping up a warning dialog staying your particular browser is not supported would probably be more effective, since then you could more casual visitors, and entice them enough to return with FF3 later.

agreed, I have basically sworn off of firefox except when I need firebug(works better then the chromium version). Making me use firefox probably means I will never even try it out.