Where in Italy would you like to go? The country is very different depending upon region. There are Marriotts in Rome and Milan, but the one in Venice isn't worth considering since its out near the airport.
If you're planning on Tuscany, there aren't any Marriotts.
I can probably help more with an idea of how long you'll be there and what you most want to see.
I would really recommend the Marriott in Monte Carlo!
From there you can drive to Como, or anywhere along the coast.
I stay in Chiavenna (Hotel Conradi,Best Western) and love the Lake Como area. Have driven to Monte Carlo many times and you should take the Professors advice and consider staying in Milan as well. You could use points in both Monte Carlo and Milan.
Go to the insiders and look up what others have written about Italy!
Good luck and Happy travels!
Just got back from 17 days in Italy, Grand Flora in Rome, Apt. in Florence, Hotel in Venice, Marriott in Milan. Both Marriotts were great Rome was nice, Florence is a great walking city. Venice was like you were in a post card I loved it, Milan was ok lake Como day trip was really nice easy train ride. Eurostar train from city to city was easy and nice. Florence day trip to wine country was wonderful day had a case of wine shipped home. We took over 500 pictures. For an apartment in Florence check out www.italyperfect.com. We went in beginning of October weather was perfect.
I recently stayed at the Rome Central Park. It is out of the way in the suburbs but if you are using points, you can save enough to take another trip.
The hotel itself was quite nice and the rooms were large by European standards. Best of all was the super air conditioning, which is essential equipment in Rome during the summer.
I walked past the Grand Flora while in the area and thought that while it looked nice and was conveniently located, I'd rather save a hundred thousand points and stay out of town.
For what it's worth, Venice exceeded all of my expectations. I stayed at a wonderful B&B called Ca' Bonvicini and highly recommend it.