On Intranet we only test with Firefox because it is on everyone's computers. I'd at least support IE8 and above for a public website, using CSS3 PIE, because I refuse to use ghetto images layouts to do stuff CSS handles fine.
Anyway, this really feels like feels a bit like poetic justice for all the times "unprofessional" developers use/used non-standard IE features or proprietary browser plugins like Silverlight that "punish" users for daring to use non-Microsoft software. Welcome to the club. Cheers.