Well, I'd surely would like to know what changed...
The fact is that I had several problems with "whining" coming out from my headphone jack after some random system sound (beep, adium message, etc) that would go off with another sound, and back on, and off, and so on... Seemed quiet but in high pich. It pissed me off, specially when I had the system connected to my stereo (perhaps I still have a decent hearing).
But now it´s gone... Well, not gone, but has really become quieter (almost inexistent)... After the update, to do the same as before I *really* need to crank the volume up on my mac and amplifier (to a level were the amplifier also produces noise).
Even if that was just it, I´m happy! Very happy!