Hi Dan,
When you apply a Object Level Restriction on the user, the user is not able to see the obect in the Objects pane atall. Nor the Column if the object is already included in the report. It does not matter who the creator of the report is...when viewing the reports it will take the report viewers rights into consideration.
On the other hand, if the 'same' report is viewed by other user who has the right to see this object, then he will see the column just fine...
Also, it does not matter which report or how the user is viewing the report.
Hope this clears your doubts...let me know if you still have any queries.
Sujit Honrao