Although I am disappointed by the current speed of Atom, I have no doubt it will improve. I think it is the most exciting OSS IDE out there. We hope to slowly converge on JS+Flow as the main front-end language at Facebook, and it will be a huge win to build tooling in the same language as the product.
Before you would have to run all these in the background + have your IDE open (ie. Sublime Text).
Of course Sublime Text has plugins itself now too, but you get the idea.
I like Sublime Text because at it's default, it's just a text editor, and then _I_ turn it into the IDE that fits my flow and current technology requirements. It becomes an IDE completely customized for my project.
(Also thanks for your work on PHP STH)