Do any of these JavaScript frameworks have decent documentation yet? API docs are all well and good, but I'd really like some examples other than to-do applications. All they really need is an equivalent to the Rails guides at http://guides.rubyonrails.org, which are ample.

Frankly I'd take any example application over a to-do app at this point.

As an aside, I've been using Sammy.js (http://sammyjs.org) more than most of these other frameworks lately, as the effort involved is disproportionate to the rewards unless you're building the entire frontend in JavaScript. For any less-than-enormous project, you really don't need all that complexity.