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I'm really not trying to turn this into a Slackware vs Gentoo royal rumble. I don't believe Slackware should aim to be Gentoo and vice versa. I'm just highlighting what I perceive to be Slackwares' weak points.
You mentioned Swaret, I've used it, and my conclusion is that it is still at it's infancy and not nearly as robust other well known package managers. Believe me, I'm being kind with these statements.
If anything, Slackware should at least focus on its security department. It is embarrassing that one of the oldest Linux distribution doesn't have a hardened channel. As an experienced Linux geek, I can deal with the poor documentation and absent package manager, however the absent security features is unforgivable.
Hardcore Unix administrators will pass on Slackware just because of that unexplainable glitch, despite the popular misconceptions.