To me it's really interesting, because it's (as much as anything else) a new metric for measuring participation, and a metric we can extract additional metrics from (e.g., session length).
As part of some related work on /reader/ sessions, I wrote a pile of code to handle session reconstruction. I've generalised it (it doesn't care if you've got reader timestamps, editor timestamps, or best buy receipt timestamps) and thrown it up at
https://github.com/Ironholds/reconstructr . I figure it could be useful to any researchers or community members looking into sessions.