If one sets the preview to be by "line" and then slides the slider, the nozzle moves far too quickly and uncontrollably around the model such that it's impossible to figure out what it is doing.
SUGGESTION: add jog controls of the form
<<< << < > >> >>>
which represent different forward and backwards speeds when browsing by line.
Much of the point of this browsing mode is surely to be able to analyse the way the nozzle is going to navigate a given slice plane in order to make changes if appropriate. It would be nice to be able to to do this!