I believe breadcrumbs should be implemented on all secondary pages because when you navigate too deep the left navigation truncates to only show parents and children and users may be disoriented. Mac suggested they only appear when you navigate deep enough but I feel it should be consistent.
You don't know what section you are in. The header tells you what main section you are in but that is simply due to the design. Currently we rely on site visitors to renavigate the structure from the main drop-down navigation or expect them to be smart enough to click the top term on the left secondary navigation.
Great idea as a standard!