I'm not sure about negativity and disinterest being "most" of the reaction to Dart. From people who actually take the time to learn a bit about the language, the reaction is mostly positive in my experience. Dart is growing, but unfortunately at this time that growth seems to be linear rather than exponential. It will likely take a major (non-Google) app being built in Dart, inclusion in Chrome, or inclusion in Android for it to really take off.