I yet again ran into this issue just recently when I forgot to reduce the speed above the infill for a print. I thought I would share a picture to better illustrate how bad this problem can be. The picture is of the same part printed with exactly the same print settings, with the exception that the one on the right was printed with a 50% speed reduction just for the single first layer above the infill. Both were printed with 5 top solid layers. It is readily apparent on the left part that, even after 5 top layers, the surface quality has not recovered after a poorly printing the first solid layer over the infill.
What happens for this one first solid layer is that the filament bead frequently breaks and/or doesn't adhere well to the infill, then curls and sticks up above the rest of the layer. This ruins the subsequent layers as well as the nozzle runs into the spikes sticking up.
