Okay the 30mm reference wasn't that clear in retrospect, so I'll try to explain my thoughts here
An 85mm lens is more likely to suffer camera shake than a 30mm one at a low-ish shutter speed, hence it needs to be faster to ensure the same level of sharpness and lack of motion. In this respect, a 30mm f1.8 is more likely to render a sharper image at a low shutter speed, i.e. 1/30th than an 85mm f1.4 one would, bearing in mind the inverse rule-of-thumb on focal length & shutter speeds dictating a 1/85th sec ideal min shutter speed for the 85mm
In practise then, the 2/3rd stop difference is less than the difference from 1/30th to 1/85th; meaning that if the shot has to be taken at 1/30th you stand more chance using the 30mm than the 85mm of getting it sharp
Now consider the actual image taken. In almost any album these days the largest photo is likely to be less than A3, and probably nearer A4 in size. On a 10mp camera or above, that's about native resolution size at 300dpi, so no enlargement is made at all. Most inner church shots are also unlikely to be used this big, so in making them smaller we're throwing away some of those expensive pixels anyway. With modern pro-end cameras a 1/4 of the image size will still produce a very good A4 print and years ago a pro showed me a 20x16 he'd made from a 3p camera and it was easily acceptable
In reality then, we can crop into a 10+mp image a long way, meaning we can effectively get a wider lens to produce an image in much the same way as a longer focal length does - especially where it's a smaller than A4 use too. Of course we don't do that if we can help it, but at lower shutter speeds it's 'safer' to use a wider lens to ensure no camera shake and crop it, than to risk a slightly blurred shot that needs no cropping
Also, a wider lens cropped at f1.8 will give more depth of field than a longer lens at f1.4, so if you want the couple both to be as sharp as possible (assuming they aren't always on the same plain), a wider lens cropped will give the more usable image
My final point then is really that although the Nikon f1.8 isn't as good as the f1.4 version, it's still a very good lens indeed. I really doubt if any client, and even most togs, would ever look at an image and think 'he should have used the f1.4 instead'
That said, if you think you need an 85mm lens and have the extra dosh burning a hole, then buy the f1.4
Ken Rockwell has an interesting point here too, the 70-200 f2.8 VR is obviously an 85mm too, and as the VR bit can save 2 stops of camera shake, you're about there with it anyway but benefiting from the greater DoF at the same time. Now if the f1.4 was also a VR!!!
You may not agree with the above, but at least I hope what I meant is clearer now?
It will mostly be for weddings (inside poorly lit churches etc) and portraits. I have the 50mm f/1.4 but sometimes need more reach, obviously as a prime it will need to be super sharp like the nifty fifty and most reviews seem to bear this out for both versions but I have seen some adverse comments on the quality of bokeh on the f/1.8.
