I've had Windows 10 on ARM running in Parallels on my M1 MBP since the Parallels Tech Preview, and have continued to be impressed at how well it runs. I've been able to install a handful of 4-8 year old apps I was pretty sure I'd never be able to use again. Windows 11 came up as an update and so far it's been running just as smooth as Windows 10 has been. All of my same apps are still working just fine. No crashes.
I had re-used an older Win10 License I had used for my BootCamp Partition on my older MBP, and now everything still shows as being licensed under Win11. To those that say Microsoft doesn't license Windows for ARM, whelp... The license I'm using was purchased years ago.
It's my understanding that the Windows shell itself in Win11 is basically unchanged from the latest Win10 Dev Previews, though. Lots of spit & polish, but under the hood it's not much different. Microsoft has explained that they plan on releasing new features via Software Updates in the future and are currently concentrating on stability, which explains how well it's running this early on.
Also, to those commenting about how Windows has worked so well on older equipment, that's because Microsoft has been lowering the bar for TPM to 1.2 up until now,
and with Win11 will be hard set to TPM 2. Yes, folks with some older computers can make BIOS changes to accommodate, but what about those non-tech-savvy folks that don't want to mess with that? I'm sure a BIOS update could be implemented to change that, too, but BIOS updates can go horribly bad if done improperly by someone that doesn't really understand.