As from Traktor update 2.7.0 up until 2.7.3 (at least) many both Mac and Windows users have issues with the sound quality.
The problems vary and depends on the files format of the tracks, so not all of us have issues.
Native instruments replaced the audio core of Traktor with a new one, giving all sort of issues.
Up until today (April 11 2005) it it’s advised to keep using 2.6.8 because that is currently most stable version.
Unfortunately some consoles will only work as from 2.7.0.
For more details about the audio problems I experience you can watch my video recording right here on You Tube