I recently looked into React and Knockout at work, as previously we had been using JQuery for all frontend stuff. I'm not much of a frontend developer, but I found things to like about both React and KO. We aren't making single page apps, but we do need to create more rich user interfaces in the browser. I spent a week exploring both, creating two different UIs in each.
For environments where you don't have dedicated frontend people, I think Knockout is more approachable. I very much like the flow based programming ideas behind React, but in the end I think the need to either learn/implement the Flux architecture or having to follow chains of Javascript callbacks really dissuaded my coworkers from supporting it.
KO has a more familiar template-like approach. And now that the latest version also offers components, I like that I can use templates where they work and switch to components when necessary, which should eliminate some of the boilerplate I faced in React. I'm very excited to try out the new KO features, and I'm always surprised to not see much mention of KO in front end discussions at HN.
That being said, while working with KO there were times where I created bugs that would have been impossible or difficult to create with React. But I think for a team of backend developers that don't do much frontend work and who aren't that familiar with functional programming, React (whether callback property style or using Flux) is too much of a jump. For personal projects I'm interested in trying out React+Flux, though.
I absolutely adore KnockoutJS, it's completely changed the way I write JS (I'm not a huge fan of or user of javascript) and 3.2 has added component support (with templates) which for me is a huge bonus as I was doing something similar manually.
I love knockout as well, however, I would love to see something like this added. Not having to declare all bindings and just auto bind to a form would be pretty useful for small stuff like single page forms.
