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I meant anger - just short-hand for "haven't used it on anything live". I've played around with demos etc but haven't used it personally on live projects. I believe they're doing what's called bandit optimization in the statistical literature. Fascinating area of study. I like it from a mathematical perspective - though I prefer declaring a specific winner and then implementing that version rather than always having the split-test software running and serving up variations. It feels tidier, easier to maintain and results in a faster website...