Originally posted by @iampun33t and @Nic2112 and then modified by me, I guess this needs to be reposted every 45 minutes or so:

1. This is OOS Open Beta 1. It is based on final Android 10 from Google.
2. There is no release date for stable version. We are guessing 3-6 weeks.
3. This is only for OnePlus 7 and 7 Pro. It will not work on the 5G Model. T-Mobile customers will need their SIM unlocked or they won't have cellular data after installing OB1. If you just want to test, WiFi will work.
4. Installing Open Beta from stable will not wipe your data.
5. Moving from Open Beta channel to stable WILL wipe your data.
6. Stable 9.5.11 will not get an OTA for this build. You need to download the Open Beta installer and install it via local update. If you're on T-Mobile firmware, you will not have a local update option. You will need to install international firmware first or use TWRP to install.
7. The downloaded file needs to be in the root of the internal storage (moved from Download directory and top of internal and not in any folder)
8. If your downloaded file has a .jar extension then rename it and remove the .jar part. The file needs to be in .zip extension to work. Do not unzip this file. If you are having installation problems, post a screenshot of current file location so we can help you.
9. The Open Beta will not get the Stable update. It will get Open Beta updates even after Stable is released.
10. As this is an Open Beta, it has some known and unknown bugs. Some banking apps will not work. Be ready for it.
11. The list of bugs and features and all instructions and download link is in the first post of this thread. Read it.
12. If at any time you have Qualcomm Crash Dump mode, hold the power and volume up key for 10 seconds. Phone will reboot automatically and you'll be fine. This is a known bug.
13. People are experiencing excessive battery drain with OB1. This is a bug with Google Play Services (just look at its drainage in battery settings) and is happening with other phone models as well. This needs to be fixed by Google and is not an OB1 bug.
14. Feedback/bug reports in this thread are welcome, but also use the links at the bottom of the first post to ensure that OnePlus sees your input.
15. As thread title says, this Open Beta is for OnePlus 7 and 7 Pro. Do not ask for update information for OnePlus 3/3T/5/5T/6/6T.

Important notes:
There are 2 major models of the phones grouped in this forum, each with multiple variants. That is about a dozen possibility so a problem reported by one user might not apply to your specific model
When people report issues, they rarely specify if they are rooted or not and if they have customized their installs. When it comes to stability, there is a big difference between stock, and stock/rooted/bunch of Magisk modules installed. Customizing increases possibility of problems
Lastly, not everyone did a factory reset after the upgrade which is known to help
So when you read about an issue, chances are the person reporting the issue has a different phone setup than you; the issue might not apply to you or you might have issues that others don't.

More info about Open Beta Program from Head of User Experience Design:
https://forums.oneplus.com/threads/oxygenos-beta-program-explained.469761/