This tangentially captures something that is important, but which I think deserves a much more prominent mention as an explicit goal: providing a "blessed" set of libraries that is large enough to be useful for many common programming tasks. In fact, I'd even suggest that the goal not just be to round out the collection of useful libraries, but that they be "good" according to criteria of efficiency, quality, and documentation, too. For instance, the Platform is currently missing a library for XML processing, but the obvious candidates on Hackage don't (in my eyes, at least) meet most of my criteria of "good".

It might be that identifying those gaps in "well roundedness" would be a helpful step towards encouraging the more focused development of suitable libraries, which I think would be a very good piece of fall-out from the Platform process.