Nerd alert: ON.
Here in my office I have the beefy printed edition of Paul Oskar Kristeller's Latin Manuscript Books before 1600: A List of the Printed Catalogues and Unpublished Inventories of Extant Collections staring at me, and telling me, "get to work!" If you need access to this work, it's now on-line (link). Happy hunting for the manuscript that breaks your stemma!
Nerd alert: OFF.