I've been running unstable for a couple decades now as my desktop. I've occasionally taken months-long forays into other distros, but always come back to Debian. It just works, which is what I care about.

It's great. Not much else to say. You install it, it works, it doesn't stop working unless you break it. I run Debian 12 on my laptop.

It works well, so long as you don't mind your DE being a bit behind the latest version. With how much Plasma and Gnome have been improving in the past couple of years, that may matter a lot.

To be honest, I think it makes more sense than it used to. You can have an extremely stable base, and if you want regularly updated user apps you can utilise Flatpaks.

I have many times. apt install whatever desktop environment you want is usually a one-liner, and they are the un-modified stock versions, not themed to whatever fancies the distro maintainer. It has been my low-effort distro for a lot of years for any purpose. Packages are on the stale-side, so you might want to use different package container types for your preferred applications nowadays.

It works great with Plasma desktop