The US PS Blog‘s confirmed that PS3 Firmware 2.43 is now live, but only PlayStation 3 users in Japan are required to make the update. From the site:
Unlike previous updates, firmware v2.43 is specific to the Japan region, and only PS3 users there will be required to
install the update. PS3 users in all other regions will not be prompted to download v2.43. However, if you manually initiate a firmware update by clicking on “System Update” under the XMB’s Settings icon, the v2.43 update will be available, regardless of where you are located.
Users outside of Japan do not need to perform this update if your PS3 system software is on version v2.41 or later. However if you do perform the update, it will not cause any issues with your system or add any new functionality.
Get it anyway. It’s fun to watch it download.