If you liked what you saw, you should try it again soon. There core editor components were rewritten in React, which lead to some noticeable performance gains:

http://blog.atom.io/2014/07/02/moving-atom-to-react.html

Beyond that, there are also more performance optimizations coming:

https://github.com/atom/atom/pull/3154

The only two things I miss from Sublime are "find in project" and "go to symbol in project". Atom's implementations of those need some work. But everything else is as good or better than Sublime. And it's really easy to contribute and get pull requests merged.

As far as I can tell from watching development, GitHub has at least 4 full-time engineers working on Atom.