Rental or No Rental ???

Is your trip a TOTAL of 11 or 12 days? In Italy you mention 6-7 locations, then you want to add 3 more countries. If in fact you have a total of 11-12 days (does that include your travel days?) you are trying to do way too much. For the places you mention in Italy you would be better off using trains. As far as a car in the other countries, be advised that if you rent in one country and return in another you will pay a hefty drop off fee.

"we meet him in Rome to then go on to S. Germany, Austria, Switz." If you planned to visit cities in those areas, OK. But if the Alps are on your agenda, April is the absoulte worst time of the year.

thanks Tom.... yes it will be late april returning to US 3 May.

Mike, I also feel that your proposed Itinerary is FAR too ambitious. Visiting "Pisa, Cinque Terre, Florence, Assisi, Padua, maybe Siena" in a time frame of five days is not realistic. Also, visiting Switzerland, southern Germany and Austria in your six remaining days is also going to be difficult. That's an average of two days per country, with no allowance for travel times. IMO, you need to so some serious pruning to your Itinerary. I wouldn't bother with a rental car, as travel to each of the places you mentioned is easily done by train. High speed trains will also be faster and more efficient, which is a benefit for such a rushed Itinerary. No car can travel at 300 kmH, so I'd recommend using fast trains whenever possible. Good luck with your planning!

You would do well to take a train from Rome to Florence. Then rent a car as you're leaving Florence for the countryside. You can see so much more with an automobile in Tuscany, as few hill towns are on train lines. Buses can be a hassle. (FYI: Your planned itinerary for Tuscany is a little aggressive.) Turn the car in at a suburban location in Florence, and take a train up to Munich. Hertz has a location at 60 Sansovino, two miles from the train station. After you tour Munich, pickup another rental car as you leave that city for the countryside. It's a very short drive from Munich thru Bavaria down to Tirol and Western Austria. You can make a circle and turn the car back in at the Munich Airport.
I prefer to rent through AutoEurope.com, and often get a Hertz car at a lesser rate than directly from Hertz.

With 11-12 days total I strongly recommend staying in Italy, especially since you express interest in so many destinations there. There are countries in Europe where a car is definitely called for, and those for which train only is preferred. For us, a car tends to be a bit of a hassle. The more experienced I become as a traveler, the more I look for ways to travel by public transport only. (That said, I have driven in eight or nine countries in Europe). Italy is a train country, in my opinion. This is a function of the trains being economical and convenient, and the driving being fairly crazy in places with any sort of traffic density. Also be aware, picking up a car and ping off in different countries will cost you a small fortune. As a rule, for smaller towns two nights should be a minimum. Rome is good for four or five nights and you will have barely skimmed the surface. Florence, I would recommend two full days. Siena, two nights (one full day). We actually did Cinque Terre as a day trip from Lucca on our 2007 trip to Italy. It worked great though I would have preferred to stay overnight for a couple of nights. It takes a lot of discipline to slow down and experience fewer places more deeply, but it's a good idea.