A PS3 firmware update rolled out this morning, very much out of the blue. It's maybe not surprising, then, the update is apparently minor, at least based on PS Japan's synopsis.
According to that, the 4.40 firmware's main features are improvements to system stability, and updates relating to the Sony RC-S380 card reader device
and its compatibility with the PS3. As soon as we have full details on the update, we'll let you know.
[Thanks to everyone who sent this in]