We used Trenìt! to plan our Italy trip both before and while we were in Italy. It worked perfectly!
The Followed Trip feature is fantastic, I'd often update a trip as we were on the train so we'd know when our stop was coming. This feature also informs you of any delays (or early arrival) of your train. That's so useful when you're waiting at the station since the only way you know your train is by time and track. Speaking of track, TrenìtfindTrainsinItaly knows which track your train will be on, a fantastic feature at any station.
When planning, you enter your start, destination and time and TrenìtfindTrainsinItaly accurately shows your choices with price, time and transfers.
One time, TrenìtfindTrainsinItaly showed a better and cheaper train than the Trentalia ticket machine at the station, so we went to the agent, showed him the listing in TrenìtfindTrainsinItaly and were able to purchase the ticket through him
We never used the purchase ticket feature (preferring paper tickets) so I can't comment on that.
The ads shown were unobtrusive and easily ignored.
Great app, a must for train travelers in Italy!