I usually wait a few weeks before installing a new macOS version. I was hoping to get automatic switching for AirPods, but that didn't happen. Here are a few of the things I've experienced since installing Big Sur:
Bluetooth: Cannot connect any Bluetooth devices (Resolved)
Sound: Cannot output sound to AppleTV or any other device. Only internal speakers work. (Resolved)
Contacts: Duplicated all my contacts and contact groups.
Contacts: Removed all contacts from some groups.
Contacts: Removed some images from contacts.
Mail: Removed the grouped Junk and Archive folders from Mail.
Music: Removed all my Music album artwork (this is a serious issue, with over 3,000 albums and over 22,000 songs)
Finder: Quick Look doesn't work at all on images, PDF, Excel or Word documents, as it used to before Big Sur.
Spotlight: Quick Look doesn't work on Spotlight items in search results.
So far, I'm not impressed.