[bitwize]

Not just cooling -- the G5 drew too much power to be viable in one of Apple's growth markets at the time: laptops. The Intel Core chips were based on the Pentium M microarchitecture and so already had power characteristics that were suited for laptop use.

Of course, POWER would go on to be a great arch for desktop and server use, but that wasn't enough for Apple after the G4.

[warrenm]

Excessive power draw ... which, while seen in abysmal battery life, was most directly seen in an inability to cool