Correct me if i'm wrong but, as opposed to canon, i think (and i have read a number of reviews that confirm this) there is a minimal difference in the build quality of the nikon 1.4 and 1.8, and both have a metal mount and similar build materials.
Unless there are several 50mm F/1.8's out there, I don't think so. I have the 50mm F/1.8 and its all plastic in terms of casing. The price also reflects this at under $110 (I found mine NIB for $105 shipped to Canada last year).
HERE is the F/1.4 at $300
HERE is the F/1.8 at under $110
There is a lot more to this than just the aperture differences.
I kinda also disagree with Early... manual focus has nothing to do with it being brighter. Assuming you can focus as accurately as automatic (which I highly doubt, especially when you are trying to catch something quick), the exposure will be identical with either picture. In real life, manual focus is a PITA to get right...
especially at F/1.4, and this I know from experience using my 30mm F/1.4 Sigma. We're talking razor thin DOFs! A hair off on the manual adjustment could easily mean blurred eyes... and this is not something you can tell using most modern digital camera viewfinders. You'll see it when it's too late... after you bring the picture on your computer screen.
As far as the F/1.4 being sharper at F/2 than the F/1.8... I cannot say for sure. To be fair about this, you would need to have the 2 lenses side by side and do your own tests... however, based on build quality, I would think that the chances are pretty good that the F/1.4 is sharper. It is, after all, near 3 times the price.