Greetings. By using the latest windowblinds beta (which skins firefox successfully at last) Direct2D support is disabled, no matter what. You can easily check this out by going to about:support. When windowblinds skin firefox Direct2D acceleration goes to "False", but if you exclude firefox in window blinds and restart the app, then Direct2D switches back to "True".

I've also tried using the option "skin this app even if it uses direct 3D" in the exclude options with no luck.