The scenery in Italy isn't quite as stunning as that in Turkey, partially because it looks a little more like it belongs on Earth than some of Turkey does. Nevertheless, Italy is a beautiful place, and was one of my favorite places to cycle. I particularly enjoyed the scenery in Tuscany.
Not surprisingly, there are some good Greek and Roman ruins in Italy. Some of the most famous ones, however, aren't the most impressive to look at. The Valley of Temples near Agrigento, Sicily, I found relatively unimpressive, though it's one of the most famous Hellenistic ruins in Italy. If you like art, though, Italy is full of good museums. Florence is particularly jam-packed with good places to see art, including the Palazzo Pitti and the Uffizi gallery.
Milan apparently got snow this year, but as I understand it, that's pretty unusual. Sicily is fairly warm all year round, and the whole of Italy is sweltering hot during the summer. I did encounter a fair bit of rain even in the summer, though, particularly in Rome.
When you've just come from Turkey, Italy seems really expensive. If you had just come from the UK, however, Italy isn't all that expensive. Youth hostels are about $12/night, but often do not have kitchens. Camp grounds are like in Greece: cheap if you're with other people, expensive if you're alone, becuase they charge both by the tent and by the person. Food can be either very expensive or very cheap, depending on what you get. You can get a fantastic meal, particularly if you're with other people and you split several dishes, for $12/person, or you can get a cheap meal of some kind of pasta for about $5. Expense in Italy, however, changes dramatically with where you are. The rule of thumb is the further south you go, the cheaper it gets. Sicily is cheap, as are southern cities such as Napoli, but Milan and Venice (particularly Venice) are quite expensive. An ice cream in Venice costs $2 or more, in Napoli it's closer to $1.10 or so. Of course, you'll also pay more in the high season (summer) than low season (any other time).
It's a good thing I was cycling around Italy, or I would have gained about 100 pounds. The food is out of this world, and relatively cheap for the quality. If you want to go to Italy just to eat, go to Napoli. The food there is particularly good and particularly cheap. I got a deep-fried pizza ("pizza fritta"), which I never saw anywhere else, for about $3, and it completely stuffed me (it would have fed two people with small appetites). Of course, as if a pizza weren't fattening enough, this one was then deep fried in oil... but it was GOOD. I've never had better food than I had in Italy, and never better than I had in Napoli. Ice cream (gilato) is also something that nobody should leave Italy without trying. It's totally unlike American/northern European ice cream, and it's absolutely wonderful. It's quite addicting. One word of warning: take-away is always cheaper than sit-down dining in Italy. There is almost always a "service fee" of a dollar or so added on to a bill when you sit down for a meal.
The Italians have a reputation for being rude, but I'm not exactly sure why. In Rome, as in any large city, the people are always in a hurry and not all that keen to serve you, but on the whole, I found Italians to be very friendly. If you speak Italian, of course (I spent some time at an immersian school in Italy), they'll be even friendlier. No matter how friendly the people are, if you can't speak a word of their language, you're not going to make any meaningful connections with them.
A note for women: Italian men can be incredibly rude and pushy with women. I would be very hesitant to travel alone as a woman in Italy, particularly in the south. The machismo is thick, and their respect for women small. They can be VERY romantic, but don't expect them to respect you in the morning.
Italians are fairly clean people, in general. The youth hostels are not always well kept (some are downright disgusting, like the one in Napoli), but most hotels are very clean. When I was in people's private houses, they were almost always immaculately kept. Italians are very particular about their water, though, and it is virtually impossible to get them to serve you tap water in a restaurant. If you order water, you will pay for it.
Northern Italy is fairly hilly, whereas the south is fairly flat. Sicily is fairly mountainous. From Siena down towards Rome, I rode 188km (~111miles) in one day, because Siena is about the last of the northern hills until you get down near Vesuvius.
Roads in Italy are good, but the shoulder is often very narrow. Drivers drive fairly quickly, and Italians have a reputation for poor driving, but when you've been in Turkey or Greece, Italian driving seems incredibly civilized. Italy is a beautiful place to cycle, though it can be quite hot in the summer. (In the heat of August, I drank over 8 liters (2 gallons) of water per day, and hardly ever had to go the bathroom.) One thing you will notice cycling in Italy is all the stuff that people throw out of their cars. Most prevalent were audio cassettes (which I picked up and listened to; it was a great way to get free music) and pornography. I was lucky not to get too many punctures in Italy, but there is a fair bit of glass on the roads.