My family and I had a great experience on a RT to Chicago last summer on the CL and the Pennsylvanian . This summer, we are thinking about going to Toronto for a long weekend, and are seriously considering taking the train. The primary reason for taking the train is to see the scenery in NY along the Hudson River and points west of Albany.
Another routing to consider would be the Adirondack Train from NYP, along the Hudson River and Lake Champlain to Montreal, then take a VIA Rail Corridor Train to Toronto the next day.
This would take an extra day, but if you have time it does add an extra city well worth seeing. Also, the Adirondack Train is considered one of the most scenic runs in all of North America, and is highly recommended.