I've been using Windows 11 for a couple months now (I first downloaded it as a beta through Windows insider).
On my main machine (Ryzen 5800X + 32gb RAM), it's been a fantastic experience. Everything just worked right from the get-go.
It's similar enough to Windows 10 that there isn't a huge learning curve, but in typical Windows fashion, they do move some settings around that serve no purpose other than to frustrate the user. For example, the system applet in Control panel has a whole new layout (admittedly they began this in later versions of Win 10), but luckily all the usual functions are there, just in different places. So takes a bit of getting used to, but this is a very mild change IMO.
My biggest gripe is that they removed the option to display ALL notification icons. Now you have to open the "overflow" and manually pull out any ones you want to display all the time back onto the system tray. That's a pretty minor issue, so as a whole, I'm extremely pleased with it and I like the new eye candy and polish.
I just got done installing it onto a much older machine (10+ year old HP Z600 workstation, dual 6-core Xeon CPU w/ 48GB RAM) that I use as my home mediacenter. When I created the USB from Microsoft's media creation tool app, it wouldn't install because I don't have secureboot or TPM 2.0 on this machine. Simply said my machine didn't meet the minimum requirements. There is a work around, however:
You download the .ISO file off Microsoft's website, and use Rufus (latest portable version) to create a bootable USB using the ISO you downloaded. In the Rufus app, there is a checkbox to "disable Secureboot and TPM 2.0 check". Once you do that it will fire up just fine and allow you to run/install Windows 11 old older machines and any that still have MBR partition tables. It picked up all my drivers except the one for my Radeon RX 480 got installed during Windows update (which I later updated to latest version from AMD), everything appears to work just as good as it did in Windows 11, super slick. I don't see a dramatic increase in disk usage, think the full install of Win11 was comparable to Win10.
Product activated just fine even though I didn't type in a product code. I'm pretty sure Microsoft is pretty much giving Windows OS away now, I've never bought a license for this particular machine, yet it always digitally activates just fine. I bought the machine used with no OS, so maybe it has a record of the old Win7 OS it used to have before I bought it; who knows. I've built brand new PCs where I didn't purchase a Windows OS/license, and they activate just fine too.