I just got the update about an hour ago, so it really is rolling out. Takes a few minutes to install and two reboots/restarts with the last one being a bit slow (another few minutes) followed by "Optimizing apps" just like a phone does. My watch was fully charged and it took 7% of the battery to perform the update. Strangely, I had trouble getting it connected to the phone after, I had to try a few times.
I see the new "Play music" and "Bluetooth Devices" options. When I go into the latter, it sees my phone as "Disconnected" even though it is connected, and lists a few other available devices.