Irritatingly slow when zooming in/out or changing from one segment of the map to another - A couple of times I've missed a turn when just using it as a map (not following a route) and it started to update a few blocks before the right corner.

But I realize I actually don't have the StreetMap III - I have the StreetMap Colorsomething, the previous model (that doesn't have the autorouting or voice). I don't know if they updated the processor.