And speaking of Custom Firmwares, 3.90 M33 is now out, M33 custom firmware catches up to latest 3.90 release - PSP Fanboy
I think putting the Custom Firmware on my PSP was one of the best things I did, some of the homebrew is amazing (iPhone style youtube) and emulators for almost every console around.
If you need any advice feel free to PM me, I've gone through most of unlocking on my PSP over time and the current way of doing it is probably one of the more inconvenient methods, but is impossible to fail with as the method is also a way of "unbricking" the PSP if it does go wrong.