You can't terraform that which has no terra to form, Willkill. Although we don't know Jupiter's mass 100%, all signs indicate that it honestly has no solid mass to it, and given its temperature, some scientists believe that it was a star that simply didn't quite get the mass needed to ignite.
Mj pretty much summed up my feeling exactly, it's really difficult to decide between natural beauty and making ourselves infinitely more comfortable. I suppose the decision to terraform would depend upon what we intend to DO while we occupy the planet and if we truly intended to populate the entirety of it.
I can only hope we'd have learned how to lessen our negative impact on the planets by the time this is a consideration, otherwise we'd just be destroying planets in our wake.
I guess you didn't see my "jk =P". Not just that ...even if it retained its current size and it were a rocky planet we would be crushed by the gravity.
I did some brief studying of Jupiter a few years ago while working on a Sci-fi novel which never actually materialized, and that sounds about right. The outer layer is gaseous and comprised mainly of Hydrogen and Helium, but there is indication of some sort of solid core within based on the gravitational forces present. We just have no way of probing that deeply into the planet.