Two more:
1. IMO, using a container to group and space controls in a toolbar is much nicer than using a separator.

2. Containers of controls can also be used in grids. In 3.0 it's a bit rough looking, but in 5.0 I think it works rather nice. And the container I had used check boxes, combos, and even a mini-grid.

>I am not sure as to what sort of applications the CONTAINER and
>SEPARATOR classes could be used for.