Big yay for me.
I'm on a 27-inch 2020 iMac (with 32GB of RAM) and Big Sur flies on this thing. While there are definitely still some minor rough edges, it honestly seems less buggy than the latest version of macOS Catalina (10.15.7) in my experience over the last couple of weeks. Luckily, most of the software I use has already been updated to play nice with BS. I dig the look and it's running super smooth and snappy.
I did, of course, do a complete erase of my hard drive and a clean install -- which itself was kind of an ordeal because I've never had a Mac with a T2 security chip. So I had to update via Software Update first, then do a hard drive erase and clean install via macOS Recovery. It's a lot of work with reinstalling apps fresh and moving files back over from my backup, but I always do a clean install with upgrades like this. I make a day of it. It might've worked just fine with Software Update, but I get more peace of mind this way.
And after a rough start, I'm really liking the Music app on Big Sur as well. I have a large, 60K+ song local library with embedded artwork and metadata and I don't like iTunes/Music futzing with with my tags. I also disable iTunes Store and Apple Music streaming service in the preferences because I'm only interested in my local library and don't want to create any potential conflicts. After a disastrous first try at moving my library back over, it's been pretty great and less buggy than I experienced with Music on Catalina. But that first attempt...
The first time, I moved over my entire Music folder from my backup, Music Library file included, as well as my Music preferences files (to their places in my Library/Preferences folder). That was a disaster. Music wasn't showing my embedded artwork for everything and there were a lot of other littles things that weren't right. So I deleted every iTunes/Music-related file (from Music/Music, Library/Preferences, and even Library/Caches) and started completely fresh. I moved all my music back over by dropping everything into the Automatically Add to Music folder and letting Music handle Music Media folder organization (on by default). Yes, now I had to manually recreate all my playlists and redo all my app preferences, but at least now I had a smooth-running library with no problems or strange behavior -- and all my artwork was showing up, for every album and every track!
So, yeah, there have been some frustrations getting everything set up properly (mainly just the act of doing a clean install with a new Mac with a T2 chip and getting things right with Music), but once I worked that stuff out, I've really been loving Big Sur and it has been running beautifully. It might be my favorite major Mac OS release in years.