iTunes 7 is a complete disaster.
My G5 is steaming to an Airport Express box, which in turn is hooked up to my $3000 Paradigm speakers.
I played the same audio files from version 7 and 6, and there is quite a big difference. In iTunes 7, there is hissing and background noise, not to mention very sharp and piercing bursts in the high (tweeter) range. EQ on both is set to flat.
The gapless playback seems to work for some albums, but not others.
One huge gripe I have...