Wanting the "engine" of emacs but the interface conventions of vim, I've been using emacs with Evil (https://gitorious.org/evil/pages/Home) a bit lately, and quite liking the combination. It implements a fairly good portion of vim, enough to cover just about everything I regularly use, which was a pleasant surprise (I'm used to "vim compatibility" layers usually being pretty shallow).
I don't use the last four of the features you're mentioning, but I can confirm indeed that syntax highlighting can make things terribly slow with large files and/or complex languages (I'm a Perl 6 guy), so yeah if multi-threading can help, I hope it gets implemented soon.
I think vim could be more responsive.
This slow response problem is only reason for trying other editor. Please make this real.