This is "Arch is unstable" thing is very much a myth pushed forward by people who only dabbled with Arch once or twice then had it break, then completely dismissed it as unstable. Without first learning how to use it even at an intermediate level - not even expert.
I too had Arch break when I was a newbie but I learned quickly how not to and it's been incredibly stable ever since. Not worse than Debian and more so than Fedora in my experience.
In retrospect my actions which had broke it originally had little to do with ArchLinux itself but a general inexperience with Linux and over-eagerness when using beta software (which you have to opt in to, it's not default with Arch).
The end result is that I've come out of it a far better Linux user with skills highly applicable to Debian and other distros. It's a far easy place to learn Linux/Unix properly and become familiarized with the OS/dir structure/config than any other distro.