FW 2.43 available in Japan; does nothing, apparently
Sony have launched yet another firmware update. There are however two reasons why version 2.43 is different to other recent upgrades:
1. It's region specific; designed for Japanese PS3s only
2. It seems to do absolutely nothing
Of course we know that point 2 isn't really true. There will be some bizarre issue that only affects Japanese hardware which is fixed with this release. Outside of the Land of the Rising Sun, there's no reason to install this if you happen to find it on the 'net.
The good news is that if you do bring your US or PAL hardware up to speed it won't harm it in any way. Or improve it. So if I were you I wouldn't bother at all.