It doesn't improve the editor's functionality, but sales and adoption wise I think it would go a long way. Especially on the Mac.
Specifically:
* The file browser is really odd. Very non-native. No in-line name updates. Odd sliding around of items coming in and out. No drag and drop. It works, but it is death by a thousand paper cuts.
* Find results tab - also really odd. It's a real buffer, you can edit text in it - but it doesn't change the source material. Just the result tab. Very odd.
* Split windows are great, but the grouping in the sidebar is odd. What's group 1 vs group 2 vs group 3, etc.
* The color scheme is ugly. Very few text editors on Mac default to light text on a dark background. The dark chrome tabs are odd.
* While I love how flexible the configuration settings are, rooting around in a .js file is kind of a pain in the ass. Some basic scaffolding that throws up a configuration dialog [that looks native!] would be great. If for option discovery, if nothing else!
* If you have split panes active, there is no way to quickly tell which tab has the cursor. Each split has a set of inactive tabs and a single active tab. It's hard to figure out exactly which tab has the cursor if you're flipping back and forth from a terminal.