Ok, I have to admit R-Mix does have some issues. Not unworkable, but bothersome.
First, I already had my midi read ahead set to 500ms (GOOD catch bvideo) so that's why I wasn't having any dropout/audio problems when using R-Mix. However, the project I was working on where I used R-Mix developed a bad latency problem with one of my soft synths. I finally tracked it down to R-Mix which was being used on a completely different track that was just an audio wav. Turning off R-Mix on that track solved my latency problem on the soft synth track (actually, tracks, it was affecting all the instances of my synth). My workaround was to apply the R-Mix to the audio track, bounce it to a fresh audio track, then delete the R-Mix from the first track. Now my audio track is the way I want it and all latency issues have disappeared. Anyway, it seems that there are still some issues with R-Mix that the Bakers need to look at.
Best,
Rob