Vuescan focuses the scanner before scanning like Nikon Scan does, right? I noticed that Nikon Scan has a plethora of setup and calibration options that I fear I would lose out on in Vuescan.
Vuescan will autofocus at preview, scan, both, never, manually... It's your choice. It will also calibrate the scanner whenever you click 'Scanner - Calibrate'.
It is missing some features from Nikon Scan, but it has it's own versions of ICE, ROC, GEM... and some features that Nikon Scan doesn't have.