I'd be very interested to hear how other folks do it, but we generally use our nurturing programs simply as a vehicle for our content. The Engagement Score doesn't tell us a whole heck of a lot beyond "more higher is more gooder," but we still use that as a rough gauge for whether or not the content hit the sweet spot of relevance and curiosity. Typically, we score in the mid-range with a few outliers on either end of the spectrum. I also subscribe myself to the same basic engagement program perf report you described above, so I get that in my inbox every Monday morning without having to sit and way for it to load.
The in-depth reporting comes from our content programs. Each of our assets (white paper, article, case study, etc.) lives in it's own program with landing page, smart campaign, etc.. We track membership in those, take a look at the LP Performance report to get a sense of how well the individual LPs are converting, and even have smart lists that are filtering program members by their referring source (email, website, FB, LinkedIn, Twitter, etc.). We're also able to attach program costs to each individual program/asset for ROI analysis down the line.
If it doesn't look cool, you're probably doing it wrong.
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