Trenitalia has just completely revamped their web site, and also introduced some interesting special fare offers for advance purchase on certain trains and certain routes. Some of the discounts are available only in 2nd class, and require purchase well in advance. One offer gives a 15% discount and requires a 7-day advance purchase. That's less advantageous than the Amica fare, and makes me wonder if the Amica fare will be phased out.
They also have a new discounted fare for one-day round trips on the AV trains, but only on routes that take longer than 3 1/2 hours. That seriously limits the usefulness, because if it takes three hours to get somewhere, you're unlikely to want to return the same day. It probably is designed for the Rome-Milan route, which is trying to cut into Alitalia's business on that route.
You can see some of the novelties on this site:
The train schedule page has been improved in some ways, and has an easier way of choosing round-trips. However, one thing I miss is that it no longer has the "details" link, so there's no way to see intermediate stops.