We converted to (&) because of its incredible terseness and general lack of use across hackage. For DSL purposes, to me it is key that this operator be as succinct as possible and (&) is remarkably underutilized in haskell libraries today, due to the fact that (|) is taken by syntax, and our C-inspired brains tend to pair them.

That seems fairly convincing to me. Count me as a +1 on Yitz's original proposal of & *or* on |> instead, whichever wins in the court of popular opinion.