Currently, if you are viewing the information page for an individual Activity within a Project, there is no easy to get directly to the Project Plan page. You just have to expand the Navigator and Browse to the Project Plan. And even then, you start at the top of the Plan, and still have to try to locate the correct Activity.
There should be an option in the Actions menu on the Activity information page to "View Activity in Plan" (or "Show in Plan") that would take you directly to that Activity within the Project Plan page.
This would make it much easier and more efficient to investigate the Project by jumping between the Plan and the Activities.