My own experience in Italy, playing as Mr. Pope on ironman, I have conquered almost all of Italy within 100 years (current date 1547, but I haven't taken anything in Italy for a decade), have kept up on time with admin (albeit with admin focus), took Administrative ideas as my first group, followed by Influence and Aristocratic, and am now the largest nation in Europe by development. I do not have a coalition, although this is due to outraged nations fearing my overwhelming power too much to try to fight me. I have Byzantium and Albania as vassals, Albania having been fed Hungary and any Balkans minor I could attack, and Byzantium about to get all of its cores back in five years when I invade the Ottomans. All in all, I feel I could have done all of this slightly faster, since I am ahead of time, but I did want to avoid that coalition as well.
I would say that Italy has become much easier to play, especially if you hate coalitions wars (I do), since most of the states remove themselves from the HRE, making them easy pickings.