Flashed it on mine and Timeline works like a charm now.
Great work from the Pebble team which kept their promise to bring the new software to their original watches, too.
It's fast and feels good, despite the watch model is available for some time.
If you update you'll experience some differences on how apps are handled. You can now invoke or use all apps you have installed on your phone. Gone is the 8 slot limit. I assume it just transfers the apps to your phone when needed, instead on before. That's nice and convenient. Same for watchfaces. You can select all watchfaces saved on your phone.
On Android you'll need to keep the old Pebble app installed, despite it is not needed anymore. To upgrade you need to install the "Pebble Timeline" app. That's the one you will use in the future then. Since some apps are making problems if the old Pebble app is not installed, it is highly recommended that you keep both for the time being. Pebble will inform you if it's safe to remove it.
Once you've updated there is no (official) way back. The recovery will also get flashed.
