Too much in too little time ?

I am of the opinion if you have to ask, you know the answer. It will depend a little bit on how much you want to see and do at what pace. You could do it but I would not. As is often stated, everything you change location you will lose at least half day if not more. You could quick get a nice overview of those locations with idea of returning at another time to more leisurely enjoy the sights and culture of each area. The second time we return to a city it always seems to be more enjoyable since we have a little familiarity with the city. You could do 3-Rome, 4-Florence with a day trip to Sienna, 3-CT, 1- Milan. Although Milan is worth a couple. Cut Florence to 3 and add 1 to Milan. Keep in mind that the first day on the ground will be marginal because of jet lag. And CT is an area and not a town so decide where you want to stay in CT.

Doable!

Rome - 4 nights
Florence - 4 nights (excursions to Siena & Pisa+Lucca)
CT - 2 nights
Milan - 1 night (pinch a night from Rome if you want a 2nd here)

It would give you a good taste of Italy... minus Venice... For a first trip I would rather spend a little less time in a location and see more places, then to end up in a place for too many days that might not be my favorite. I would try to work in Venice and cut Milan if possible. Depending on how you travel (train?) I really don't consider it 'lost' time.... you still have it:) Just because you aren't trooping around a museum does not mean you can't enjoy it. Picnics on the train, writing in your journal, enjoying the countryside and villages from the train, etc. I would probably do Rome 3, Florence, 4 (day trips) and CT 1 nite and add Venice 2 and last nite in Milan. A bit of a whirlwind, but still very doable...

Very doable!

You just need to ask yourself (honestly) what kind of traveler you are. Are you the kind of traveler who is looking for a relaxed holiday where you return refreshed and ready to get back to work? Are you the kind of traveler that approaches a trip almost as a challenge to see the most possible and return needing another vacation? Somewhere in between? In my experience, folks on this forum tend to lean toward one end or the other. What's best is what works for you.

For me (and unfortunately if you ask some members of my family) I tend to learn more toward "adventure" than "relaxation". We did Milan, Venice, Florence, Sorrento, Rome (with quick stop in Bologna and Naples) in 15 days and loved every minute.

joanne,

That doesn't look like "too much" at all. It should be easy to work out an Itinerary with those four places. It won't allow a lot of time in any of them though. You might arrange the order Rome > Siena > Florence > Cinque Terre > Milan.

You could squeeze in Venice if you wanted an intense experience.
(I would choose either Venice or CT however)
Rome - 3 nights
Venice - 2 nights
Florence - 3 nights (excursion to Siena)
CT - 2 nights
Milan - 1 night

As a first trip to Italy, I would fly into Venice and out of Rome. Skip Milan entirely.

Possibly -
Venice 2-3 nights
Florence 3-4 nights, with trip to Siena
Cinque Terre 2 nights
Rome 3-4 nights