FUD. I've had several developers over several teams pick up Backbone significantly faster than 1-2 months. I'd strongly recommend over generalising from personal experience, and perhaps considering why Backbone has so many devs using, and contributing to, it.

I've been writing MVC apps in JS and ECMA script in general (eg AS 3) for a good time now, and have used other MVCish frameworks before (Dojo, Flex etc). Backbone has a solid implementation of models, views and events. If you understand the fundamentals of Javascript (knowing event listener closures are references that'll prevent GC) and write modular code you can do great things with it without any "mess".