Well I've owned all 4 of these personally, and the only one I still have is the 50mm f/1.4D. But take that like a grain of salt because for all I know our styles might be totally different.
I loved the focal length of the 35mm, but for the natural light shooting I was doing indoors, when it came down to it f/2 was just plain too slow and I couldn't get the shutter speeds I needed at any reasonable ISO on my D80. Same thing with the 50mm f/1.8D. That's a fantastically sharp and contrasty little lens which looked better off the camera than the 35mm f/2, but a little too long and not quite flexible enough, and the bokeh was ugly. The 85mm f/1.8D was great too, but again the bokeh. Yuck. Some people confuse ability to isolate a subject and get a tight depth of field and "bokeh" as being the same thing when they're not. All of these can deliver very tight depth of field, but bokeh specifically refers to HOW the out of focus area light points are rendered. The 50mm f/1.8D and 85mm f/1.8D both have quite ugly and harsh bokeh that has well defined edges and a "rolled condom" sort of look. That's NOT what you want for creamy smooth backgrounds and you really have to be careful. You can get creamier looks, so long as you don't have any brighter light points or a complicated pattern in your background. I would have kept the 85mm f/1.8D, but for tighter head shots that I like to get, the 105 or 135mm primes are much better, and again the ugly bokeh on Nikon f/1.8 lenses these days. The 85 makes you get too close for my tastes, but take that like a grain of salt too because everybody has varying comfort levels for how close they mind getting for tighter head shots. The 85mm f/1.4D which I have
NOT owned or shot with has much nicer bokeh and is one of Nikon's very finest lenses. But it's $1000.
I may still buy one of these one day, but I don't love the 85mm FL enough to warrant spending that much money.
So now I have the 50mm f/1.4D. It gives me the extra bit of speed I need to get those indoor low light shots, the bokeh is nice and creamy and not distracting at all, and I just deal with the fact that it's a bit shorter than I'd like for some shots. It's a nice short tele on my D80, and a fast "normal" prime on my F100 film camera so it gets good use. The only thing I don't like about the 50mm f/1.4 is that it has contrast wash out issues when you point it into brighter light sources, as do a lot of other f/1.4 prime lenses. This is the ONLY lens where I actually use a hood, and it does seem to help a bit. I've been getting better results with this lens since I've started using a hood.
Bokeh, it goes like this:
35mm f/2D: OK, neutral to slightly harsh in a very harsh test
50mm f/1.8D: ugly
50mm f/1.4D: nice and creamy
85mm f/1.8D: ugly
85mm f/1.4D: nice and creamy.
In fact on another forum the 85mm f/1.4D has the nickname of "Cream Machine". It also delivers marvelous skin tones. The bokeh on the other lenses was pretty much a known quantity elsewhere except for the 35mm f/2. I had one and just happened to do a comparison and posted it once upon a time so here's what it looks like. This was an EXTREMELY harsh test that will really exaggerate this.
35mm f/2 @
f/2
35mm f/2 @
f/2.8
35mm f/2 @
f/4
35mm f/2 @
f/5.6
For the most part, edges are not sharply defined with a "ring" look, but they don't fade out smoothly either. So overall I'd rate it as fairly neutral, which is good enough for my purposes. I avoid any lenses that have harsh bokeh characteristics.
If portrait work is mainly what you're after, I'd consider just getting a "Beast", Nikon's AF-S 28-70mm f/2.8 lens. This is the discontinued previous version of the current 24-70mm f/2.8G, but the reason I'd recommend trying out a 28-70 is because it's said to have even better skin tone rendering than the current 24-70. It's also a lot cheaper and fairly easy to find used.
