I am using the Nikon 50mm F1.4 AFD and used to own a Nikon 50mm F1.8 AFD before. I found both sufficiently sharp for normal prints when wide open if you get the proper focussing point and techniques right... I heard about the D90 having focussing issues with the Nikon 50mm F1.8 AF-D before but I cannot comment as I have not owned that camera before...
Here is a sample wide open picture taken with Nikon 50mm F1.4 AFD, looks sharp enough for me...
http://bokehman.blogspot.com/2009/06/i-did-casual-photoshoot-with-this.html
Here is a sample wide open picture taken with Nikon 50mm F1.4 AFD, looks sharp enough for me...

http://bokehman.blogspot.com/2009/06/i-did-casual-photoshoot-with-this.html