I think he's done an incredible job making a stable, secure, fast operating system that makes sense. I've tried really hard to use Debian/Ubuntu/others but always come back to Slackware after scratching my head for hours wondering "which file do I edit to this?" when the answer is actually "which distro-specific script do I run to do this?"

I'm extremely biased because I've only ever used Slackware seriously (for servers and desktop) but trying my best to put that aside, I think it's a masterpiece.

There's a cred to it too, which is no reason to use something, but it's the icing on the cake. In some of my support jobs, I had to interact with other techs, and once in a while you get a BSD snob who says "Oh pff, you're into linux? What distro do you use?" and after hearing "Slackware" the tune usually changes: "Oh! You probably know what you're doing then." I think it's true, though: if you can manage a Slack server, you can probably manage any server. The reverse is probably not so true.