Outside of Gunboat, I've played three complete games as Italy. Two were Full Press, and one was Public Press. Here are my experiences.
1.
gameID=67307: "Get Down"
This was my first game as Italy, and among my first Diplomacy games in general. During the course of the game, I ended up in a very tight-knit alliance with Austria. We essentially took on a Juggernaut together while France and Germany were busy fighting England, and through much coordination we came out on top. We then took on EG the same way. The alliance was sufficiently fulfilling that we agreed to a 2-Way and actually saw it through. It remains one of the few games I've played where the possibility of a solo was outweighed by the quality of an alliance.
What I learned most from this game was that, when Italy and Austria actually get along and can trust each other, they are a very potent pairing. Especially when Italy focuses on fleets and Austria on armies (the Austrian fleet was destroyed early on).
2.
gameID=85261: "Sargemarcher's Public Press Invitational"
This game. Oh man, this game. 21 years of Public Press mayhem. We more or less all hated each other by the end of this game, with Russia deeming me the most obnoxious Diplomacy player on the site. Good times.
But yeah, I soloed this game. An interesting challenge, essentially convincing [enough of] the entire board to let you win in plain sight, but I pulled it off. How? Well, I started by turning public opinion against the "Wicked Witches" of England and Turkey, making a strong alliance with Russia and Austria to take out Turkey while FG tried to beat up England.
England survived by virtue of a Western Triple forming to take on the AIR Alliance, but Turkey was already toast and we proved more than a match for the WT. The combined Western powers only had 7 SCs left when Russia stabbed Austria and I in a solo bid. I rallied everyone against Russia, and we crippled them before infighting resumed once more.
I took advantage of the fact that most of the players really hated each other by this point, and the Western powers in particular had fantastically poor relations. I convinced them to cut out England, and following that made a solo bid myself. I eventually succeeded, mostly thanks to the fact that I was continuously able to put the remaining powers at odds.
This was another game where I had a strong alliance with Austria, and while he did make every effort to stop the solo at the end, we still got along better than most of the other players. My solo, interestingly enough, did not include a single Austrian Home Center. Nor did it include any of Austria's common neutrals (Serbia, Greece, Rumania). Rather than stab Austria, I more or less just kept stabbing other powers until Austria felt compelled to do something about it. I then mostly just fended him off while diving into the cluster&*#$ that was Western Europe.
3.
gameID=94180: "Triathlon Full Press"
Austria and I didn't get along so well this game, so I killed him. He was out in 1902.
Predictably, this resulted in me going head-to-head with a Juggernaut immediately afterward. Things looked bad, but I held together long enough for the West to get their act together (which took a while). The alliance was effective enough to get Turkey to stab Russia, at least, and the focus from then on was thwarting Turkey's solo ambitions. This was successful, and resulted in an uncertain enough balance of power that we agreed to a 5-Way.