I upgraded my H@O2's firmware half an hour ago, and when I plugged it in and opened calibre, I got this amazing error notification:
"calibre, version 3.35.0
WARNING: Failed: Kobo database version unsupported - See details

Your Kobo is running an updated firmware/database version. As calibre does not know about this updated firmware, database editing is disabled, to prevent corruption. You can still send books to your Kobo with calibre, but deleting books and managing collections is disabled. If you are willing to experiment and know how to reset your Kobo to Factory defaults, you can override this check by right clicking the device icon in calibre and selecting "Configure this device" and then the "Attempt to support newer firmware" option. Doing so may require you to perform a factory reset of your Kobo.
Device database version: 149.
Device firmware version: (4, 12, 12111)"
I say amazing because it was clear and helpful and explanatory, thanks! I wanted to ask if, "HSD" warning notwithstanding, there is any real risk to selecting the "attempt to support newer firmware" option in the extended driver?