See http://caniuse.com http://caniuse.com for specific features. IE9 isn't awful and IE10 will be better, but IE10, which will be released next year, is anticip

See http://caniuse.com http://caniuse.com for specific features. IE9 isn't awful and IE10 will be better, but IE10, which will be released next year, is anticipated to have less support across the board than other browsers have today. That imposes a drag on use of new features, because of the need to backfill with js-based emulation or to provide alternate implementation of features that don't depend on tech IE can't handle.