Got my M1 MacBook Pro yesterday. Setup has been more interesting than past machines. I initially tried to configure it by restoring a backup from a Time Machine drive, but got an error that for some reason the new Mac couldn't read the backup. So I then used the migration tool to copy from my old Mac, which took about 3 hours. After that everything seemed to be working except for a few licensing issues tied to the hardware ID on the previous machine. I decided that since my current machine was four years old I'd be better off starting from scratch, and I wanted to re-install all my apps anyway since they all needed to be updated to support the Apple hardware. That's when the fun started.
I booted into System Options (which is a different process on the M1 hardware - rather than holding down option-R on boot up, you hold down the power button). I then erased the hard drive and tried to reinstall Big Sur. That gave me an error that I was unauthorized to install Big Sur. Apparently the new Macs have a new security system that ties the Mac to the Apple ID I provided on initial setup. There's a bug in Big Sur so instead of giving you a chance to enter your username/PW, it gives you an error.
There are a couple of work-arounds - one is to go into iCloud and delete the machine, the other was to open terminal and use a command to reset the password, then re-erase the hard drive. Once I did that, I was prompted for my Apple ID/PW to reinstall Big Sur.
After the reinstall it automatically downloaded my files from iCloud, but the default setup is to keep Documents and Desktop as local folders, not synched to iCloud, so they were both empty which caused a mild panic attack. It's a fairly easy fix to tell the Mac to use iCloud as default documents/desktop folders, so that's fixed.
The only other issues were with activating Office (I don't have a subscription to O365 and so I had to reset my license for Office 2019 with Microsoft to activate it on the new machine.) And I have one other old software package for work that required changing user permissions and applying two patches to get it to license and boot.
So far, I haven't really noticed any difference compared to my 2017 MBP. Safari is a bit faster, but that's about it. The battery life is supposed to be between 12-17 hours so that will be nice if I ever start traveling again. The keyboard is a bit better but I use an external keyboard and touchpad so that doesn't help. The biggest downside is that this model only has two USB-C/Thunderbolt ports whereas my old MBP had four. The only way to get four on a MBP now is to buy one with an Intel chip.