I see no reason why the two Italian players will not beat Vinciguerra. Vinci is basically off and on with playing and hasn't been a top performer for years. Although none of the Italians are great on hard court, they are all (the 3 potential singles options) better than Vinci at this point and should win. So to me it comes down to the doubles, where Italy is the major underdog. It will be an upset but Italy can do it, hopefully they make it happen.
I agree with your reasoning on Vinciguerra, and while an upset isn't out of the question, I do think it is improbable.
Yes, the court is poison for the Italians, but you have to ask how much does it really favour Vinciguerra? He has barely played this year...doesn't have the match fitness and confidence an average touring pro has, and surely his physical fitness is a little suspect for a distance match?
Soderling surely won't lose either singles matches, so the Swedes would only need one more point. They have two decent doubles specialists for Saturday...certainly on paper they easily outclass the Italian pairing. The only concern is that Bolelli and Bracciali could be tough to break if they serve well, and if the tie is nicely poised at 1-1 after Friday, a few moments of Swedish panic (Aspelin...) / Italian inspiration could swing the tie a little in Italy's favour.