I have already bricked it last month by installing 3.1.1 Beta 4. It took Apple 10 days to repair the Watch (reinstall the OS) and send it back to me. Don't wanna wait 10 days again.
You can get a replacement only if you have AppleCare+. Otherwise, you have to send your Watch to Apple to get the OS reflashed.
Series 1 updated just fine. I now make sure to turn my screen on indefinitely on my iPhone while doing the update so there's no funny business. I had my iPhone in the Watch app say it couldn't verify the update because I wasn't connected to the internet when downloading 3.1.1 two weeks ago, presumably due to the wifi turning off while the screen was off or switching routers for some reason (I have my own "mesh network" using repurposed airport extremes in the house). It gave me a small scare since we can't DFU restore the Watch at home. Since then I just make sure the phone is on completely until the update is done.