As you may have already discovered PS3 firmware update 1.92 is now live, and it's the best update ever. Why? Well, because the changelog wasn't released alongside the update, so 1.92 currently has the best feature of all: Possibility. A quick glance through the NeoGAF forums shows us that the update does everything from improving the internet browser to automatically powering off controllers to improving PS1 and PS2 support and heating Toaster Strudels.
So, no, we don't really know what it does at the moment. Do you have any ideas? Notice your PS3 acting strangely? Hopefully we'll know more later in the day.
Update: So, Sony released the list of new features right here. Apparently the only difference is that backwards compatibility for some PS2 titles has been improved.