Firmware 3.70 came out only a few days ago and already a new version is out. As promised by Eric Lampel, Director of PSN Operations, the new PSP firmware is now available to download. Although the regional websites have not been updated yet, the firmware can be downloaded using the [Network Update] feature. The new firmware update increases PlayStation One title compatibility and also strengthen the security of the software.
Another point to note is that the update has no affect on Japanese PSPs. We are still waiting for a official changelog and will update this article shortly.