It's pretty nice, but you don't get two-way binding for free and it's not really baked in. In your example you'd have to use an input or content-editable element and then call ractive.observe and write your own code for binding user-input to your model data.
Compare to something like Knockout.js where you don't write any special code to get the two-way binding (other than creating each data field as an 'observable' field.)
Much like Javascript's "==" operator gives you type conversion for "free", it's not clear to me that getting two-way binding for "free" is a good thing. One-way binding is significantly easier to reason about.
Most of the time, data binding IS one-way when using Knockout.
Input field? That's one-way from display => a variable in your viewmodel.
P tag? That's one-way from variable in viewmodel => display.
But when do you really need two-way data binding? Form validation and formatting. Man, this stuff is hard even with two-way data binding. You have to be able to accept, parse, format, and validate all in the same element. It's very helpful to be able to use knockout for a task like this.
> In your example you'd have to use an input or content-editable element and then call ractive.observe and write your own code for binding user-input to your model data.
I thought about moving to a system that uses React or something like it and I looked at a bunch of them, but I'm sticking with Knockout for now because it lets me keep my markup in the HTML document where I personally think it belongs.
I'll probably end up moving to Aurelia (or something like it) because it's so pluggable and you can use it with React or not. There are so many choices right now, it's hard to decide!! Sticking with whatever I pick is also sometimes difficult, but I've been using Knockout for about a year now.
Compare to something like Knockout.js where you don't write any special code to get the two-way binding (other than creating each data field as an 'observable' field.)