Although it's not showing up at cros-omahaproxy.appspot.com, 0.12 is being pushed to the beta channel as we speak. Once again we have beta channel and dev channel on the same version again for a few days. It's likely that sometime next week we'll see dev channel jump to 0.13 with the new 2.6.38 version of the Linux kernel.
With just one month to go until Chromebooks hit retail channels, it seems likely that 0.12 will receive a few stability patches in beta channel before being declared the first stable channel release of Chrome OS. In terms of features, we know that Enterprise support is enabled in 0.12 (but not on Google's server side yet for regular accounts). Also, Chromoting (Citrix / Remote Desktop support) has also been enabled in the OS but not on Google's server side for some time. The avatar image selection introduced in 0.12 (those cool waterpaint style icons you can choose for your login instead of a picture of yourself) is another sign that Google is starting to polish things up for a final release.
Chrome OS Stable here we come!