On Mon, 30 Mar 2015, Edward Kmett wrote:

Collapse the first two steps into one step, but this means that nobody gets any warning of new names coming
into the Prelude. On the other hand this would get us all the way to done by 7.14. On one hand, the first
order consequence the amount of breakage caused by adding Semigroup to Prelude and taking (<>) is almost
entirely confined to a handful of pretty printing libraries -- and we already broke those same libraries by
taking (<$>).

Btw. hmatrix is another prominent package defining (<>) for matrix and related multiplications.