I've noticed quality issues when printing something like a solid cube. The bottom and sides look great, but when the printer starts to fill in the top of the cube, printing over top of the infill, it's moving at the same speed as the walls printed at, which is causing adhesion issues, especially where the top layer meets walls - if there is not sufficient infill near the edge, the head will basically extrude a loop over open air, and the top layer will have gaps.
If there were a way to have the printer slow down when printing directly over top of infill, similar to how the first layer can be slowed down, I think the problem could be alleviated.