Oh, it's wonderful!
Daughter and I went in 2000, the Jubilee Year of the Catholic Church, but that didn't make it more special than it already is.
Don't miss Pompeii - it's amazing to see the remains and how intact some areas still are, right down to the frescoes on the walls, the way the streets are built and you can still see the grooves from the chariots in the stone street sections still intact.
Of course Venice was magnificent too. taking a gondola ride is worth it - it's a view of Venice you cannot enjoy any other way! And St Mark's is a must see while there. Takes your breath away.
If you can, visit Pisa, there is a building beside the leaning tower there is round building made of stone, once used for baptisms. You can climb, in a narrow circular staircase against the inside wall - all the way to the top. When we were there, the 'guard' if you wish to call him that who handles the building sang the scale (his voice had perfect pitch no less!) and the buildings natural acoustics gave me chills to hear his voice.
Be careful of the street shysters - you'll know who they are right away because if a Policia vehicle is anywhere around, these vendors close up faster than two blinks of an eye! They're not valid and their goods are not quality. There ARE valid vendors on the streets in some cities, but not the ones who lay out their items on blankets
All except the major cities like Rome or Milan, you'll find that there are few vehicles in the streets, many of them cobblestone still, especially the side streets. People walk in the streets, giving you a feeling of a truly (and in fact it mostly is) a pedestrian lifestyle, especially in the older smaller cities.
Most of the cities have piazza's, or town squares. Wide open spaces, usually cobblestone or brick, these are left over from a time when people gathered there for town business, news and such. Very charming and a great place to sit along the edges of and watch the people as you take a break.
They have wonderful little shops off the beaten path, side streets which are narrow and shops of which are so small it's amazing to see.
We had a tour guide which helped, she was fluent in English, Italian, Greek and French. She would connect us with various people who would talk the history of various places we would visit. It was incredible to know the history of churches we visited, places we went to see.
Oh, one warning. Hotels in the smaller cities, and yes, even in Rome, were retrofitted (if at all) with elevators

And they are tiny! Don't take big luggage, you may have to hoof it up the stairs to your room

We saw that more than once, where a large piece of luggage and one person could not fit in the elevators!
We were there in June, so I'm not sure about fall temperatures. Look into that and try to pack as lightly as you can unless you plan to stay in one hotel your time there, moving the luggage due to the tiny elevators is something to keep in mind.
Of course my having been there 10 years ago, I'm sure there are changes, but given that there is no room to build in many areas, I don't think you'll find much has changed in accomodations. One thing that was interesting is that almost all the hotels rooms are pretty unique, not standardized like we have in the US. Old buildings that were converted to hotels and therefore, each room is different from the next

Very nice, as long as you get a room that doesn't have a bathroom so small you can't move in it
Some of the rooms we had were like suites they were so large, bathrooms huge etc. Some, not so much

Fortunately we never stayed in one hotel more than 2 nights before we were headed to another city, another part of Italy. We covered a lot of the country in 10 days!
Hope this helps some. Enjoy! The people are friendly, gracious and suffer well any attempt at speaking Italian you might be willing to try
Oh, one more oddity. There is no ice in Italy, unless you find a modern American icon such as a McDonalds. Water and drinks served are room temperature, very difficult to find fredo (cold) drinks most places.