If something "takes some getting used to" then it is new and unfamiliar, and people will need a considerable amount of time before they are accustomed to it and comfortable with it. It's a set idiomatic expression that you can just treat as a "unit", but it breaks down like this: "takes" = "requires" "some" = "a considerable amount of" "getting used to" = a noun phrase derived from "to get used to", meaning "to become accustomed to"
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