Today the 1.2.0 version of Knockout was released. Check out this postfor details on the changes that are included. I am very excited to not have to keep saying this feature was not in the 1.12 release, you will need the latest code! Lots of great improvements in 1.2 including serious performance fixes, new bindings (event, attr, and html), and my personal favorite new feature, writable computed observables. I think that this is a really solid release and I look forward to the future of this great library.
The 1.2.0 script is available here. If you are working in Visual Studio, then you can also get it via NuGet (Install-Package knockoutjs).