I know what people mean, but I've bought two um2s for work and they been very reliable, never need recalibration, and we put about 100 hours print time a week on them. I'll see if I can get a um3 ordered, it would be nice to see if they've done dual extrusion reliably. My own um2 is still working well I've not recalibrated the print bed in 6 months and it stills just prints well, although it's not perfect, my next upgrade will be a bond tech feeder or maybe a flex3drive, but other than that, I'd like to do a dual extrusion setup if it was fire and forget, I don't have enough spare time to keep faffing around..