I ran it for many years (and still do on a couple smaller machines). It has been exceptionally stable and thankfully devoid of "surprises" (using the word in its worst possible connotation). Things stay exactly as you leave them, it's exceptionally rare for any package to have been "customized" and nothing happens in the system unless you explicitly asked for it / made it happen. This used to be true for the initial setup too, which made it a bit scary to newbies - but since quite a few years that's become a painless experience.

Its learning potential is very large.

As someone once wrote:

Study RedHat, you will have learned RedHat

Study SuSE, you will have learned SuSE

Study Slackware, you will have learned Unix.