The best Italian food at WDW is Palio (though it is about to go into rehab so may not be open).
A good second choice would be Portobello Yacht Club at Downtown Disney. It's fantastic. The food is excellent and the service especially so. It also has a great martini menu.
Spoodles isn't an Italian restaurant, precisely, but Italian cusine is one of the cuisines it features. It has, over the years, been one of our favorite dining experiences overall. It's lost a bit since chef Marianne Hummel moved on, but we're still looking forward to going back.
The Italian restaurant at Epcot, Alfredo's, remains the only full-service restaurant we haven't tried, due to consistent, reliable bad reviews we've read, ever since it opened.
Mama Melrose, at D-MGM, has decent food, but service has typically been very poor. There are rumors that it is also going to be rehabbed soon. Let's hope they reimagine something better there.
Tony's, at the Magic Kingdom, is okay. The food is passable, and the service is actually very good. It's pricey, though, and for some reason many people (though not myself) seem to have a problem with the prices, there.