Ok, the shoot i did with Cayley who is on the main page of my website wearing black i was very happy with as i wanted everything in focus and it worked well. I use the 50 when i want a blurred background but it hasnt been giving me the sharpness of the subject i want (some of the time).
If I'm reading this right it's not an issue with the lens per se, it's the limitation of juggling focal length, depth of field and distance from subject of both the camera and the background. From the sound of it, what you wanted to achieve with the Cayley shot would be pretty tricky to get with the right focal length and aperture but the key thing is that that focal length and aperture would only be right for a photo with the same ration of factors. Move to a different location and the distances change and therefore the requirements of the lens change too. One right lens for one situation won't necessarily be the right one for another, or the next one, or the one after that.
Maybe this is down to me then but as i have stated and been told there are better lenses than the 50mm 1.4.
Okay, ask yourself some questions.
Why do you want this uber-sharpness?
What do people mean by 'better'?
Are these people in a position to talk from good experience or are they just repeating web forum myths?
The Nikkor 50mm f:1.4 is a brilliant portait lens.
Professional portrait photographers come in many different shapes and sizes and they use all kinds of different kit. The one thing they have in common is the ability to produce portraits which sell. I would recommend a fast (f:2.8) zoom for the two reasons I've stated previously 1) It's flexible 2) You get a variety of shots. Unless you have a very particular style and want to work with only a set focal length and certain parameters flexibility and variety are key.
I got a book on the business of photography as a christmas present last year. The only thing it taught me was how not to be a portrait photographer. The author, an american, was shooting medium format film in a studio. He used the same lighting set up time and time again, even to the extent of advocating having legnths of string so that you can measure the distance of the lights from the subject's nose. His photos are all, IMVHO, awful. Photography has moved on. Portraits are rarely static. They're taken in all kinds of locations, from all kinds of angles. These are the shots that sell, not just to magazines but in the lifestyle market too. If all your shots are taken at 85mm f:2.8 how many different shots will the buyer want? One? Maybe two if you're luck? What if they're taken at a variety of focal lengths, close up, environmental, full length. Now a number to choose from they're going to want more. This is what you want whether you selling them or not. Sure you can walk around with a prime, but all that walking around takes time, distracts the subject, you miss looks, reactions you could get by zooming in quickly.
Finally, the most important thing about portraiture is the ability of the photographer to capture something special about the subject and to translate that into the photograph. The only way that kit affects this is in a detrimental way, if the kit is intrusive say or awkward for the photographer to use.