Just came across something interesting, thought I share this perhaps this could giv some insights into potential new features. My apologies if this is something that everyone is aware of already.
chris-granger.com/2012/04/12 … e-concept/
or any of these: codemirror.net/
Adobe Brackets
WebKit Web inspector
jsfiddle.net
Bitbucket
Google Apps Script
Eloquent JavaScript
Emmet
Prose.io
Upsource
Paper.js
Codev
Tributary
WeScheme
Mergely
WebGL playground
The File Tree
JSHint
SQLFiddle
CSSDeck
sketchPatch Livecodelab
NoTex
GitHub’s Android app
More…