Sony pushing out a firmware update isn't particularly newsworthy - but in this case it's for the long neglected PlayStation Portable, a device that's more than 10 years old. Just bear in mind that the last firmware patch appeared in August 2011.
There's nothing too earth-shattering in firmware update 6.61 - it basically adds a few stability patches, so it's even more surprising that Sony pushed it out... and that they were actually working on it in the first place.
The 31MB download is mandatory if you PSPers want to carry on using the PlayStation Network, so it's probably a good idea to get it installed and benefit from those barely noticeable stability improvements.
Japanese users are the first to get the patch, with UK and US gamers set to receive it at some unspecified point in the future. Sony says not to install the Japanese update if you're not actually in Japan.