Train tickets: Buy now or when we arrive in Italy?

I traveled on both Italo and Le Frecce trains last year, in the lowest of the 4 classes, and found them both very comparable, as well as comfortable. You can book ahead if you're really committed to departure times and want to save a bit (e.g., about 20 euros vs. 40 euros for a 2nd class ticket Venice-Florence) between the big cities. But if you want to stay flexible, then it's not hard to buy ticket in the stations. Florence-Cinque Terre tickets are not sold very far ahead and you also don't have to reserve for the Milan-Varenna-Tirano route (operated by www.trenord.it).

• You will save money if you book the IC or the Freccia trains in advance. (You can do so up to 120 days in advance, typically). Purchase regionale and regionale veloce train tickets upon arrival.
• I haven't been on Italo, but many say it is better or at least the same quality as Trenitalia. Just beware that in Milan it operates out of Garibaldi and Rogoredo, not out of Milano Centrale station. It will only be an option M-V and V-F, for CT and Varenna you'll be looking at the Trenitalia website.
• There is a difference in the size of the seats between 1st and 2nd, 1st is a little more roomy. 1st is a little less crowded typically too. I don't usually find 1st class worth it, but when booking tickets for this summer the supereconomy price for premium class on a Freccia train was the same as the economy price for 2nd class (no supereconomy tickets were available) so I figured if it was the same price, I might as well upgrade.

Wow, thank you for the quick replies! Sounds like I should book the IC tickets now and get the regional ones in Italy. I've also heard the Italy Eurail passes aren't really worth it since P-P tickets are cheaper. Agree?

Point to point is almost always cheaper in Italy.