Very much looking forward to reviews of this multi-material unit. I did not care much for the Bowden setup in the older Prusa design.
How well does this new design work in practice?
https://shop.prusa3d.com/en/printer-upgrades/183-original-prusa-i3-mk3-multi-material-upgrade-kit.html
@David_Sherwood From the interview, got the impression they were chopping the filament, so no purge needed. There is at least one other design that does this. Prusa seems to be offering a lower price point.
And of course, does this work at present? 
@Preston_Bannister even if you chop the filament, you still need to purge as the cut will be above the hot end. Joel Telling (3D printing nerd) met Joseph at BAMF2018 and you can see that the purge block is still a thing. For me, it’s a thing that makes this method unrealistic. Joel, did some tests in another video and for some models the purge used more filament than the model and for many it was around 50%. I can’t afford to throw that much away, quite apart from the environmental issues, given that these purge blocks can’t even be recycled (unless it’s some sort of murky grey).
@Jon_Gritton Ah. Saw the video before, but missed where they were printing a purge block with the new design. Bummer.
Though feeding chopped filament segments through the extruder/hotend would be quite tricky. Would need an exceptionally well-constrained filament path.
Guess we are not there, yet.
I think they are still fully retracting the filament and only cutting in case of detected feeding problem.
I have that with a multicoloured nozzle
Ah. An update. Watching:
Seems Prusa is working on a purge-as-infill feature. This makes a huge amount of sense! Though … seems to need some serious integration with the slicer?
Great idea, but tricky. We (mostly) do not care about the color of the infill, so purging color changes while printing infill makes sense.
If you have multiple color changes in a layer … tricky.
If you are printing with dissolvable supports … tricky.
If you are printing with flexible materials … tricky.
Prusa to present has been mostly a hardware company. If they keep along this line, they are more a software company. Perhaps not their strength. Tricky.
@Preston_Bannister tricky indeed, what happens if there’s not enough infill to properly purge at a particular z-height? You can’t just switch to the purge pillar if you’ve not already built one to that z.
I also dislike the road they’re on of making the Prusa slic3r edition so tied into the machine’s features, I’m sure I’m not alone in having my own preferred slicer, and that can make a lot of sense when you run multiple machines from different suppliers.