The coolest update in my mind relates to the headings for the sections in the Doctrine & Covenants, including new headings for OD1 and OD2.
There's been plenty of discussion of the changes on other blogs -- By Common Consent and Juvenile Instructor are two that I subscribe to. I can add no scholarly observations, just my person observation that I'm glad I do my scripture reading on my digital scriptures, so I have these updates already on my Kindle Fire.
And the updates themselves are cool. More evidence of the care being taken in the Joseph Smith Papers project and the reflection of the work of those scholars to reflect accurately the history as best they can. The changes in the headings are not earth shattering; many simply update small details like dates. But there are some significant clarifications.
For instance, the heading to Section 89 removes the note that the first three verses were inpired but written by Joseph separate from the revelation itself. And the headings to the Official Declarations are way cool.
It's impressive to me that the leaders of the church asked for these updates eight years ago. Eight years ago! That there is an eight-year gap between the request and the published product speaks to the care and quality of the work, and the desire to coordinate with the great work of the historians engaged in other elements of the work.
How grateful I am this year to have these changes, the historical settings of sections of the Doctrine & Covenants online, and so many other resources available. What a rich and fertile field we have for our gospel study.
UPDATE: Check out this link at FAIR Blog for an outstanding post on the 2013 edition of the scriptures.