Upgraded to AppleTV 3.0.1 last night, installed the mods. Everything is going well so far! Have all features working such as AFP, SSH, full Codec support thanks to Perian, plus the new 3.0 menu system and iPhone Remote.
After upgrading to AppleTV 2.4 and installing Perian, I no longer can play Apple videos. The device just shows a black screen. Sometimes there is sound.
Edit: found a fix from westont on AwkwardTV:
Sure enough, looking in the /System/Library/QuickTime folder I found a ‘Disabled’ folder had been created. This folder contained the ‘QuickTimeH264.component’ file which had clearly been moved there by something. Moving this file back to the /System/Library/QuickTime folder and rebooting the ATV got everything working again.