1. The dither code was rewritten. Now every dither source is uncorrelated. What this mainly means to users is that when multiple dither sources (e.g. from busses) are mixed together, the dither noise floor won't be as high. Summing two correlated dither sources results in a 6dB increase in noise floor, where as summing two uncorrelated dither sources results in a 3dB increase.
2. The master fader code was rewritten in the stereo mixer to be more inline with the surround mixer, and to have slightly better truncation error performance.
3. The mixer summing bus headroom was increased from 30dB to 48dB