And yet, even IE9 has major CSS bugs.
For example, say you want rounded corners. Cool, it does border-radius!
For example, say you want gradients. Cool, it does ... well, sorta. ms-linear-gradient works fine on its own. border radius works on its own. But combine them together, and you're in for a world of hurt:
The box shadow, and border radius, show up fine. But the radius doesn't clip off the corners from the gradient - so you get a perfectly weird looking element.
I give them a B for effort, an F for actual usage.