In my few reviews of the Atom DOM for creating a theme, the structure felt very tame (and I too have looked at CodeMirror/Brackets). I found it readable and straightforward. There's a bit to it, but eh, good enough to work through if I inspect elements etc.

Sublime sure is fast. This is fast too. I haven't put it through its paces in normal usage, but at least I have a fallback that I like.

Package hell is true for anything is it not? If you're saying Atom doesn't have N feature count that matches other editors, you could very well be right, but I have a feeling that will change. Also, I'm sure Atom will start ranking plugins at some point too.