Other task runners that you should look into:
I’m currently using Gulp, for the majority of my applications. You may wonder why I switched, mainly because the cool kids persuaded me to,..LOL. No seriously, Gulp focuses on code, while Grunt is all about configuration, Gulp is a bit faster, and has a cleaner API, but by all means if you are into Grunt, stick with it.
If you write Coffeescript, then you are most likely using Cake, from my brief experience, Coffeescript, has no plugin system, so you are on your own to write tasks and from what I understand, it can get a bit arduous when writing larger tasks. It may be the best tool of choice for very simple use cases.
Broccoli is sort of like Gulp, it’s task based, has a plugin system for helpers and it relies on the command line for parameters. Unfortunately, its code base is not fully stable yet and it lacks a community, but it seems promising and I wouldn’t be surprised if it became the the next hottest task runner.