If you can get text selection (and copy/paste) working please post how you did it. I wrote Gate One which is a web-based terminal emulator. Right now I have to go through great pains to ensure that text being rendered to the screen happens in a performant way while still allowing for copy & paste functionality. It also has some features that will highlight text that you select with your mouse and other text formatting stuff.

I've experimented with canvas in the past to see if it could improve the performance of, say, a terminal that updates very quickly but it ultimately ended up being just as slow as the regular DOM because of all the extra code that had to be running in order to keep the hidden buffer in sync with what was displayed to the user.

I'd be curious to know how the performance of WebGL compares to the (accelerated) canvas.