>If you look very closely, it's a little soft, but from a normal >viewing distance it looks great.
See if you have the same problem I do with these large prints: people look at them from a proper viewing distance, say "Nice photo!" or some variation thereof, and go to inspect it up close where they can see it isn't as sharp as it could be...
That said, it's amazing that we can get anything like an acceptable result at that sort of size from the D1's 2.75 MPixels since it equates to about 115 dpi, and 300 dpi is the usual figure for being considered photorealistic.
>I used QImage Pro
Have you tried using the Lanczos interpolation to resize your images? To my eyes it does as good a job as Genuine Fractals, and QImage is one heck of a lot cheaper. It's also my favourite NEF converter by far.