Hi Jon,
Ship Simulator 2008 Pro is made for professional training use with external controls, displays, chart plotters, etc. It will also run like SS 2008 in “Sunday Sailor†mode on the same—higher end—systems that run non-pro. In beta testing on the same Vista machine that I use for testing non-pro, I see only a slight performance hit when running the same missions.
The only things it offers for non-pro use are the vastly improved sea model, and the Frigate. It also includes the Ship Dynamics Editor, which is not that easy to use unless you understand the principles behind it. For instance, there is no “Max Speed†or “ROT†slider. Those are calculated underway by the physics routine from more basic values such as hull resistance / speed curves.
With luck, the useful features will trickle down into SS 2010.
Marty