Please note the following:

A window of the given application needs to be open in any given space to get switched to it OR you need to have an application assigned to a space from within the Spaces preferences.

If you have an app running, but don't have any windows open or it isn't assigned, then you're not going to be "space warped" anywhere. It will just bring it forward in your current Space, and in the case of most of them open a new window in the current space (when using the dock to switch, that is).

You're absolutely right. I discovered this when playing around with InDesign under leopard. If I had no windows open in ID, and I clicked the dock icon for ID, it would just bring the app forward into the current space, even though I had specifically assigned it to a different space than Safari for example.

OTOH, if there was an active ID document (window), it would correctly switch me over to the space assigned to ID.