How can I get the number of vertices/triangles per object? I'm working on a scene that's getting complex: I have 30 objects for a total of about 5 million triangles. I start to be concerned about performance.
I would like to know which of the objects contribute the most to this high amount of triangles to focus my optimization efforts.

Unfortunately, selecting an object doesn't change the totals (I seem to remember it did in earlier versions of Blender). 

Is there a way (built-in or with a plugin) to display the number of vertices/faces/tris per object ?

Are there any tools or techniques that could help to analyse the performance of the scene ?
If you Tab into edit mode with the object selected, the poly count changes to the object.

Before entering edit mode:



After entering edit mode: