Google Reader tracked a lot of data about your feed reading habits, including but not limited to:

- Average items/day published by subscriptions - Number and percentage of items that you actually read - Number of items you actually clicked, per-subscription - Time of day items are posted / items are read - What subscriptions haven't updated in a long time?

You are right about it exporting starred content, by the way. None of this other data, however, is available for export.