We've recently purchased an Ultimaker 3 Extended at work, and so far we're pretty impressed with it.
One thing I have noticed is that if I build a cube (or any straight-sided part directly off the build plate) that the first layer is always a little bigger than the rest of the model, leaving a sharp ridge around the bottom of the part which throws the part tolerance off a little. I've otherwise been pleasantly surprised by how good the tolerances are on the U3E.
(This is when the 'Build Plate Adhesion' setting is turned off, before anyone thinks I'm really confused!)
This sort of initial inaccuracy is something I've noticed before on other FDM/FFF printers. I could get rid of it by rounding or chamfering the bottom edge, but is it not possible to correct for it in the printer settings? As it's quite a common thing to see, does the effect have a name?