I have one (I picked one up in less than perfect cosmetic condition for around £250) and it is a lovely lens in many ways.
View is brighter through the viewfinder - this thing sucks light in! Wide open it needs to be used with care - best at middle distances I think, where it can still isolate subject and is at its sharpest. There is a kind of dreamy look wide open which you either love or hate. Up to f2.8 I suspect it's the best 50mm of all the Nikkors, but they're all great anyway so I don't think that is a massive thing personally. Between f4 and f16 there's probably nothing to choose between them.
It can be hard to nail focus wide open, unless the subject and camera are stock still, and I suspect any inaccuracies in the position of the mirror/focusing screen are at risk of showing up with the razor thin DOF.
I'm not 100% convinced by its merits though. If you want a superfast portrait lens, you might be better off with the 85mm f1.4 (I don't have one of these beauties, but I do have an AI converted f1.8 which is nearly as nice). If you want a superfast general purpose lens, you might be better off with the 35mm f1.4 (which I do have, and which I think is actually far more useful, because while half a stop slower, you can easily hand-hold it at a whole stop slower shutter speed, so arguably it is a more useful lens for general low-light work, especially as its DOF is a bit more manageable!).
If you already have a (slightly) slower 50mm, I'd go for a 35mm f1.4 personally.
Perhaps have a look at the reviews on here, which are perhaps the most respected (if you haven't already):
35mm in here:
http://www.naturfotograf.com/lens_wide.html
50mm in here:
http://www.naturfotograf.com/lens_norm.html