i use one and it does the job. usually you would want something within the 85-100mm range which the nikon 18-105 would be ideal but ive got the nikkor 50mm 1.8 and i get really sharp photos from it. lighting is key (obviously) and thats my 2cents.
Its an excellent lens and its wide maximum aperture allows for nice shallow DOF images. The focal length is a good choice for loosely framed classical portraiture. When it comes to bang for the buck it can't be beat.
The 50mm is a little short for tight face-only shots. For these an 85mm f/1.8 might be a better choice. Zooms that cover this range can work well but none are really fast enough to produce the extremely shallow DOF that some people like in portraits.