The 1.5 firmware, eh? You all remember that crazy bastard. Japan-only smart-card payment solutions and the ability to select an image as a user icon. This is why we have wars, everyone.
Fortunately, PlayStation 3's 1.51 firmware - available wherever PS3s run free - is now available and it's a lot more laid back. So laid back, in fact, that all it seems to do is expand "support for PlayStation 3 format software titles".
Confused? Think of the PSP, and how Sony would routinely update the firmware there in such a manner that you had to upgrade if you wanted to play the latest games. This is the equivalent of that.
If you have a PS3, then you know the drill by now: pop into the system menu and update via the Internet or, if you prefer, you can download the firmware to your PC via the US or Japanese support sites.