The only information that was lost was any statistical data that was from my device that had not made it into one of the updates from Dash. So nothing that was an update was removed, but I now can search for Burger King by name. So if it was an update it is still on the system.
In other words a factory reset on the Dash Express is similar to resetting Internet Explorer to its defaults, in that you still have all of the updates installed, but all your settings go back to the default. It is slightly different because your address book is gone on the Dash when your favorites are still there for you in Internet Explorer.
To be clear the only things it deleted was from the following list, Address book, recent destinations, search history, WiFi access points, saved search entries (they require Internet to work), & any historical traffic data that was not in an official update from Dash.
I can confirm that I had data from traffic data as I went to Kirkland Washington using my Dash Express & as I was going up I saw historical traffic data on roads I have never been on in my entire life. Also if you use the 2008 map update DVD it will tell you that you are using a newer version of several things including historical data.
One last thing right before I cut the Internet off from my Dash Express I was invited to a beta test & I can confirm that I still have the beta version running on my Dash Express, as they made some slight modifications to the map screen with the beta that I was in. Unfortunately for me they didn’t release the full version before I killed the Internet on it & I didn’t have money to connect it again until after Research In Motion had decided to kill the Internet for all Dash Express customers.