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Looks like if you use Gentoo, it's not so useful for you.
But this tool may be useful to lot's of other people. Mostly, the ones learning how to install for source instead of disto packages and learning how build tools work... It's more useful for then than automation process (which they could learn to use in the future with standard build tools). It's a step-by-step tool, will help people learn and not feeling so lost in the beginning. I'm sure that lots of slackers, mostly beginners, will like it.