Has anyone taken the night train from Rome to Venice?

I'd be interested in recommendations on how to book it. Is the Trenitalia website reliable? Should I wait to consult an Italian travel agent at the risk of waiting until 2 days before we actually need the train?

We are looking to get a 2 bed compartment. Trenitalia says they have a 2 "seat" compartment, but the diagram actually shows beds, and the price is 155 Euros which I assume must be for beds. Anyone know if the Italian word "posto" can mean "bed" as well as "seat"?

Darren, Kamloops BC