Obsolete before it hit 1.0. While grunt/gulp was fun for a while... i am not looking back to our 800 line grunt file, complicated async configuration and the tons of dev-dependencies. Webpack blew everything out of the water. 80 lines of config, hot-reloading, code-spliting, hash-filenames... Looking forward to whats coming next.
Of course, the async thing (and such) is something I agree with, newer tooling has iterated and improved on Grunt.