Eurail vs purchasing tix
 

I can't answer this question directly for you, but Consumer Reports Travel Letter had an article on this exact subject within the past year. The article included extensive data on how to compare trips in specific countries. Another thing, that article talked about other rail passes besides Eurail. There are country specific rail passes which are much cheaper than Eurail. Sorry, I do not know the exact month, but it should be easy to find at your local library. Good luck!

All of your questions can be answered very easily at Rick Steves "Europe Through the Backdoor" site at
http://www.ricksteves.com/home.htm
You can request a catalog that lays out all of your railpass options and it gives you a chart that allows you to calculate the individual ticket prices based on point to point distance. My art students and I have used this guide and their railpass service many times. From experience I can tell you that you should make seat reservations if you have any time limits, as most of your routes are very popular and crowded.

My wife and I used Italian rail service last Sept, and we purchased a Eurailpass. We especially appreciated the access to first class cars that comes with this pass. Second class is often very crowded, while we always had comfortable room in the first class cars.

Last year I went from Venice to Florence and then Florence to Rome by train. The regular first-class train tickets are not expensive but needed in advance (asa by my travel agent before departure). Good luck.

I have been told by my travel agent that one can buy an Italian Kilometric rail pass that allows up to 5 people to travel a distance of 3000klm in Italy(2 people-- 1500klm each)
Have not used it myself yet.
hope this helps

I'm planning trip to Italy (part of 4-month European
tour) during May. After researching the options, I decided to purchase an Italy flexi-pass for 8 days
travel in 30. They're available there at any major train station.
Perhaps we'll cross paths. Have a great time.

I have used the kilometric ticket several times. You purchase it in Italy. When using the railroad , you go to the ticket window,give your destination and the number of travelers and they deduct the kilometers from you balance. It can be much more economical than Eurail since for non-students, second class Eurail was not available.

If you buy tickets at individual train stations in Italy, make sure you verify the ticket in a yellow machine located near the platforms. Otherwise your ticket will be invalid and you will be fined. I speak from experience.