I dev on Ruby and I am a hardcore Sublime user, which is about as far away from Microsoft-friendly as you can get, and I have been really impressed by it.
Their app store is advanced, and crucially they allow Visual Studio to be setup with key bindings that match Sublime's, meaning switching over is really easy with almost little to no need to learn new macros. IDE's like Visual Studio can allow you to do code and class refactorings that make Sublime look like a joke.
It is a great app, I agree, but it also comes with its own legacy.
Not sure how difficult extending it is, but on day one in their app store I found all the important ruby bindings I needed to replicate what I value most in my Sublime set up: i.e. ruby linting and rubocop.
The switch was so painless I hardly noticed I wasn't using Sublime -- except in the moments of joy when I found the other powerful things it can do.
This stands in big contrast to RubyMine -- an IDE I absolutely also adore for its power -- but one that I found challenging to pick up due to its custom macros.
I'll have to look into the plugin API, though. I'd have to convert a lot of custom plugins, but that could be a fun weekend distraction.
However I held onto Textmate until 2010 and Sublime wore me down, so I'm a laggard as well.
So no negativity from me, because I just want a great editor that I can control and hack on. But I'll be real, I don't see it happening for a little bit. If sublime were to support JS plugins, I fear Atom might be in trouble at that point, TBH.