Once you get the hang of it, train travel in Italy is easy. It is also a great way to see the beautiful countryside on the way to your next destination.
I have travelled a couple of times using a rail pass, but the last couple of visits have just purchased tickets for each individual trip as we went.
That said, we often have purchased tickets a day or two in advance - particularly if the particular train requires a seat reservation, or if it is a busy time of year.
Purchasing a little in advance also means that you don't miss the train you want to catch due to a huuuuuge queue for tickets...
Last trip we used the automatic ticket machines at the stations and found them excellent.
Also, I have travelled both first and second class, and didn't really find much difference - travel second class and you can use the extra money to buy more wine/food etc
Just remember with all tickets that you need to validate them in the small yellow ticket machines before you board your train.

