Big Sur Install hangs up after reboot

I began an install/upgrade of my Mac to Big Sur last night. The initial stages seemed to go ok. I left it for a while, came back and got the multi-colored new sign in screen. I clicked on my standard icon representing me as the user, entered my password and it has had nothing but a spinning wheel under my log in name for about 8 hours. Oddly, I am getting the little "take a tour" messages and something is running in the background because I actually got a calendar notice of a recurring event! But the screen is stuck with the multicolor splash, login name and spinning disk (not the beach ball).

I'm a little afraid to just power this down, but what else is there to do?