It's very noticable when you get into complex areas of music. Try comparing a 320 version of the end of Do Sum'n to a 192 version. I first noticed with the ending to 7 days.
now...the difference between 128 and 192...that's when it starts to get really noticable.
which is why it kills me when I get hooked up with rare Tech stuff by people who encode DOWNWARD from 192 to 128. (what up V? yes, I'm still grateful I'm just sayin... :knockout