I guess there’s be a blog post coming up soonish, but for me the big deal is integration of a templating language. We experimented with the MS-written templating plugin that’s now been integrated and it seems pretty good.
http://jsperf.com/dom-vs-innerhtml-based-templating/73
TL, Didn't Benchmark: Two orders of magnitude slower (approx) than other engines. On the iPad, for example, jQuery-tmpl was able to render a small template 181 times in a second, whereas Eco, at the other end of the scale, was able to render the same template 11,549 times.
Edit: I also want to point out that the linked page above is user editable, and allows remotely hosted javascript (by design). Beware :/