Will Batman have a perfectly dual-extruded face? Stay tuned for Part 2 of my Big Builder Dual Feed Review!
You can read Part 1 at http://nicklievendag.com/big-builder-dual-feed-review-part-1/
That is a very cool extruder. It looks like the slicing software is smoothly varying the ratio between the two colors, mixing them slightly in advance of the applicable portion of the print in the upper part of the heat chamber. It probably does some extra and early retraction when it needs to make quick contrast changes. We should be seeing lots of mix-on-demand nozzles coming down the road.