With a good IDE (Webstorm) and a good debugger (Chrome), you can do great stuff.
It supports tons of paradigms. You don't have to go prototypal to use OOP. Although that is the most memory efficient method in JS.
I use it a lot at work to quickly protoype stuff for mobile. It is much more convenient than writing for native Android, or iOS.
Also, firefox is including http://asmjs.org/ in it's nightlies, s it seems that performance is constantly improving.