I ran it in 2011 and it was the best race I've ever entered. Running into St Peter's square will take some beating. Unlike London, the course takes in all the famous landmarks. It pretty much takes in all the sights on any postcard of Rome. If you look at the 2011 thread, there's plenty of advice on registration and the medical forms. Bear with the organisers, they get there (eventually). For the run itself - run wearing a GB top, there's a lot of expat support which will give you a boost; and consider running with a small camera / iphone for the sights (I'm glad I did and it didn't slow me down). And Rome's not a bad place to carbo load on pasta in the days beforehand. Enjoy it!