It's been a while, but the last I heard it only worked in the U.S. Now they may have changed that but I get the feeling you'll get charged for using it if that's true.
In the U.S. you can make international calls. Don't know if it works the other way around.
I think your option is Sipdroid+GV over WIFI. The only problem I see though is the WIFI you'll get as in my opinion(experience) in Italy I had the worst internet connection in all of Europe!