Yup, I've only had it for several days, but my MK4 kit I got "just worked" after I assembled it.
I did have to take a look at it yesterday as it was making a clicking/knocking noise. Turns out the applicator took they supply to pack the bearings with grease doesn't work the best, had to repack the y-axis bearings, no more noise.
Hell, we use two MK3's at the lab I work at, and they have about 2000 hours of print time between the two of them and they're just now showing signs of wear (one of the printers had a hotend fail).
Between the fact that they're open source, they're damn near bulletproof, and that I worked with them already, getting my MK4 was a no-brainer.