I understand this has become a marketing trick for 3dprinter manufacturers, but what I'm surprised about is not seeing this discussed in forums like this one.

Who cares if the new Ultimaker or a Solidoodle with custom software settings can print at 20 micron layer height, if the minimum width of the extruded plastic stays the same 0.42 / 0.48 mm? No matter how awesome and smooth your model will look in the Z axis, the top and bottom parts of the model will have noticeable line seams.
Unless this can be changed as well and nobody is talking about it, 0.02mm or even 0.1mm is pointless to go for aesthetic reasons.