Keep in mind - the camera always focuses at max aperture. Focusing at f/1.4 gives the camera more light and a narrower depth of field for more precise focus. Low light photos are more reliable with f/1.4 even if you are not shooting at maximum aperture.
I love the shallow depth of field at 1.4. It allows me to include more of the scene without distracting from my subject. Daniel McGowan Visit my Nikonians gallery.