Mine felt like that after I did the upgrade, but after doing a clean install it feels much faster 
(more than Catalina did too - which was beginning to feel quite slow, hence wanting to upgrade sooner than I usually would).
I have to say, I love it 
While there are a few areas that need tweaking, it feels really polished - quite a lot nice than Catalina. In fact I think Catalina has been one of the most uninspiring updates in the series, Big Sur feels like they care about macOS again.
I’ve also reset my Feedback Assistant password and have been reporting a few small bugs to them. They are usually really good and I think to date, they have fixed every bug I have ever submitted - and I have submitted quite a few over the years.
The only thing you might need to do is calibrate your display as the colour profiles they shipped seem a little off (things might appear a little washed out). Not sure why but this seems to happen every few years, and again it’s something they seem to sort out.
Overal tho, I really like it!