In pursuit of getting a faster lens (than F/1.8), I paid a visit to my Nikon store today. The 30-minute play with both the Nikon 50mm F/1.4D and F/1.4G revealed much softer images results wide open, compared to the F/1.8D. The play also revealed that the F/1.4G focus at a much slower pace than the older F/1.4D (though in a much quieter fashion)!
Sweet spot is clocked at F/2.8 to F/4 for both lenses, with the F/1.4G leading in the department of Bokeh quality (due to her more rounded shutter diaphragm construction). Aesthetically, the F/1.4G win again with her more beefy, "thicker" diameter barrel of 58mm.
All taken, however, the F/1.4 aperture provides a 50% bigger aperture working space for those low-light scene. Buy it if you prefer to improve your image quality without bothering to carry your speedlight along.