I don't have a "real" Stern yet but I hopefully should soon. So far I've only used Pinball-Browser to update songs & associated text on AC/DC and Metallica for virtual pinball.
I'm guessing for real machines it would be a good idea to have 2 or 3 SD cards with modified code, official code, and maybe the prior release in case of issues. Or at least have the images backed up so they can be re-written. Is anybody using a SD card switcher to be able to more easily switch between different code?