Things I need before I'm going to pretend IE isn't a steaming pile of shit, hell I'd settle for just 1-2:
* Evergreen browser (I'm sick of dealing with 7/8/9, I don't look forward to playing the same song and dance with 10/11/12/etc)
* Cross-platform (Testing on Linux or a Mac is painful)
* Open source (IE is the ONLY major browser that is not OS, and yes I know Chromium != Chrome but I'd be fine with IE doing the same sort of thing)
Still a bit worse than the others, but Safari has also lagged lately (and Safari also isn't evergreen).
(I agree with all of the above for the older IE < 10)
Interesting, as their partner for Modern.IE, BrowserStack, uses a Javascript based remote desktop. (It may also support Flash on certain browsers, but I'm not sure about that part.)