Some feedback from my last Duke of Provence -> King of Burgundy game:
--The HRE lost most of Burgundy (Provence, Savoy, Dauphine) and some of Italy (Toscana, Pisa, Urbino) in the first 15 years, but as these lands are not de jure part of the Empire, it's fairly acceptable. The Empire even reconquered some of the italian minors a few decades later.
--Pisa conquered Corsica, Sardinia, Salerno and the remaining coast of Toscana with little to no resistence; Sicily seems unable to retake Salerno either, even after two or three wars. I myself conquered Sardinia and Corsica rather easily from them, however.
--While Pisa (and, in my previous game, Genoa) went gallore on its conquests, I never saw Venice move a finger to conquer anything.
--Iberia is an interesting place: the Christian-Muslim dynamics are very good, with both sides moving the religious borders, unifying and breaking from times to times, but unable to conquer the other side. At the current moment, Navarra took over the former lands of Castille, Leon and Galicia after Toledo collapsed, and Al-Xarq and Aragon exchange a few provinces every couple of decades.
--The crusade results are bugged. There were two sucessful crusades for Egypt, and the Pope was the main contributor in both. The result: italian counts gained the provinces, but they stayed as vassals to the Duke of Alexandria or to the Caliph, being shortly after revoked.
--Some heresies had moderate success, but eventually failed to Holy Wars, conversions or muslims. Novgorod become Iconoclast, too, and they are resisting the other russians rather well.
--England, Scandinavia and France are pleasantly stable: they had few or no civil wars, however they had major wars against the greater powers, and the results are balanced too.
--Lotharingia formed in Lower Lorraine, and they are going to incorporate Bavaria very soon.
--The Rurikovich formed the Kingdom of Lithuania, and they are unifying Russia quickly now.