Most of them.
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Debian world - apt sucks. For something with a sole purpose of resolving a dependency tree, it's surprisingly bad at that.
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Redhat world - everything is soooo old. I can see why business people like it, buy I rarely, if ever, agree with business people.
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Opensuse world - I've only tried it once, probably 15 years ago. Didn't really know my way around computers all that much at the time, but it didn't click and I've left it. Later on I found out about their selling out to Microsoft and never bothered touching it again.
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Arch - it was my daily for a year or two. Big fan. It still runs my email. At some point the size of packages started to annoy me, though. Still has the best wiki. I've never really bothered with the spinoffs, as the model of Arch makes them useless and more problematic to deal with.
I've got the Gentoo bug now. For the first time I genuinely feel ~/
. A lean, mean system of machines :)