People have already been using 333 Mhz clockspeed for emulators and other homebrew apps for a while. And maybe it's just a placebo effect, but existing games definitely feel smoother when you select the "override default clock speed to 333" in the custom firmware boot menu, and the pauses while it streams your backup copy ISO data from the memory card often disappear.

PSP homebrew and Devhook users have known about the 333 speeds for donkeys!

who really needs 3.5? when you have 1.5 ;)

This would be the same overclock that a fair amount of "homebrew" applications have been using since firmware 1.50?...

A lot of the emulators use it (megadrive etc) - it does make a difference to battery life but nothing else (heat etc)