If there was a time for Microsoft to make amends for all the bullshit we, web developers had to put up with in the past 10 years or so, it is now. Hopefully they'll catch up with Firefox and Chrome.
If you're using advanced features because you've found a use for them, but you're not using SASS and mixins (or similar), then again, more fool you
The other vendors are actually churning out progress and the burden or integrating that progress into your work is entirely optional. Microsoft can't even implement years old specs, and the burden associated with their inability to create even a bog basic browser is not optional.
[1] http://ie.microsoft.com/testdrive/Performance/ScrollingText/... [2] http://ie.microsoft.com/testdrive/Performance/TextJustificat...