Long Range Scanners are stopped by Scanner Jammers and the ever-popular Scattering Armor. So remember that you won't get a free peek at everything. Also, you can see what space stations are building.
A Last note, currently if you scan ships you haven't seen before they will appear in your "enemy ships" design list, but only for that turn. As yet, the game doesn't store those designs for you permanently, but I believe a fix for that is in the works.
