So for you few but growing number of Sony PSP owners, you are probably used to the flow up firmware upgrades. While constant firmware upgrades usually seem to signify a progression in usability, in this case it seems to be more about the fixing of hacks and workarounds.
Nothing new with version 3.1 of PSP firmware which has been released. There are two main feature upgrades/addons though. When you are viewing a webpage, the browser will now use up less memory than it previously did. And when you listen to your massive audio collection on your PSP, the volume will now be automatically adjusted to a constant volume. As stated before, this firmware is mainly about the ongoing battle against hacks to play “backup” games… — Nik Gomez
PSP Firmware 3.1 Hits [Kotaku]