CodeMirror has had a ton of work put into it and Light Table mostly rides on that. Opening a 40kloc javascript file and searching in it is totally smooth. Auto-complete, jump-to-definition etc are fast and don't block the UI. We still have performance issues in places (eg watching large directories which change often, serialising large inline results) but we haven't had any problems with the DOM being too slow. CodeMirror deals with all of that for us.
I'm playing around with React (and Om, Quiscient etc) at the moment and it's by far the nicest UI model I've ever encountered. If I could get Cassowary working reasonably fast too it would be miles ahead of anything else.
The only thing that I don't see improving soon is not having shared memory threads (or even zero-copy messaging). Webworkers are all well and good but sometimes the serialisation overhead is still enough to block the UI. thread.
I agree 100% about React - I can't help but think that an editor based upon it could really speed up all the DOM manipulation that holds back every webkit-based desktop app.
Re: Web workers, this probably isn't news to you but you can use transferable objects [1] to eliminate the serialization hiccup. Of course, if you're really trying to share objects across threads in real time, rather than transfer data, parse, and fire events, you may have bigger issues.
I'm playing around with React (and Om, Quiscient etc) at the moment and it's by far the nicest UI model I've ever encountered. If I could get Cassowary working reasonably fast too it would be miles ahead of anything else.
The only thing that I don't see improving soon is not having shared memory threads (or even zero-copy messaging). Webworkers are all well and good but sometimes the serialisation overhead is still enough to block the UI. thread.