The flexibility. I researched several frameworks for our current web application. Each has its pros and cons. We needed to have a lot of control and customization for our project and I didn't want to bloat our project with unnecessary tools.

The minimalist approach that Backbone takes. It is lightweight but still allows for modularity of code. It is also fairly easy to learn and get a decent grasp on but still allows for complex applications. The documentation is also excellent and is very in depth for how small the footprint is. One of my favorite parts is how easy it is to get off the ground running with an application. You can have one built and working within an hour.

backbone events and triggers backbone collections and models data-binding simple local storage