I have ordered from Amazon.fr (France), Amazon.uk and the Book Depository.com.uk and received my books no problem.
When the news first hit about Amazon starting an Italian website, Linda, a Canadian exapt in Milan said, "It's exciting news, isn't it! Your books may not show up but it's the thought that counts." ha.
Poste Italiane has a terrible reputation. The funny thing is, it used to be worse. I have a hard time wrapping my head around that.
We'll see. I use the other sites only for English language books I can't find here. Living in Rome, I have access to great independent bookstores and several chains, like la Feltrinelli.
I love bookstores and will always support them, even if I have to pay a little more. I can't see buying Italian books from Amazon.it but if I lived in a small town, this would be a fantastic resource.
I assume they will start to sell more international books and other products. Amazon in the States sells much more than books.
Will Poste Italiane be up to the challenge of delivering books in a timely fashion? If it goes well, maybe Netflix would be next. Now, that's a service I can be very exicted about as most of the mainstream/commercial film DVD rentals places are automated anyway.
The picture above is from a billboard near the Ponte Sisto bridge. It's massive.