I don't know much about the past, but in at least the past 3 years, Microsoft has been incredibly committed to IE development and enabling it to be more standards-compliant than ever. They've been consistently pouring money, time, manpower, etc. into making IE the best browser that's out there. This is one excellent example of the fruits of our labor: http://samples.msdn.microsoft.com/ietestcenter/

And no, I'm not speaking on behalf of my employer; it's just my personal opinion.