I found the Vatican interesting and love the museums, etc. but if I find myself back in Rome someday, I'll pass on the Vatican.
It strikes me as somewhat claustrophic with all the people. It is also usually very hot.
Mom said she'll take me to Rome when she's 75 (2013). We went to Amsterdam for a week when she was 65, which was cool.
My parents have spend a lot of time in Italy, and seen just about everything. My brother lived there 4 years, and now he's in his 6th year in England.