In reply to Fraser:
What is it that you want to achieve?
1) the satisfaction of using something that's a bit awkward and difficult, to get interesting results
2) the specific DoF and bokeh you will get from 85mm f/1.4
3) some sort of money saving
4) other
3 or 3.5 years ago I fannied around with manual focus on a digital camera (a slightly different set-up - Vivitar 28-105 f/2.8-3.8 on a Sony NEX F3) for hand held spontaneous shooting. 95% of it was out-of-focus crap. Of the remainder, I might as well have used a standard modern AF. If the D7000 has a good viewfinder you might get away with it. Years ago I had a D70 and thought it would be nice to use it mostly with an old "pancake" Nikon 50mm f/1.8 wide open for concerts etc. Again - nightmare (terrible dark small viewfinder TBH).
I've been off photography a few years and just getting back into it with a Canon 600D. I've started veering toward wanting a fast telephoto prime and I did consider a Fotodiox adaptor and an old manual Minolta (135mm f/2.8 PF Rokkor) or a Samyang thing.
In the end I've gone for a second hand Canon 100mm f/2.0 proper modern AF lens. I want to pretty much "point and click" in low light at concerts etc, and be confident that I'll probably get an acceptable image. Nikon or third parties presumably do something similar. Mine was £229 from London Camera Exchange. I await its arrival. I have a feeling that I'll regret it less than I would regret a Samyang manual thing....
Just tonight I've been rediscovering a load of pics from a festival (Green Man 2014) shot with the NEX F3 and the manual lens. Total waste of time, twice over (wasted time shooting, wasted time reviewing).
I would think that what others have said or implied about it being perhaps a studio/art lens, makes sense.
Unless your answer is "1" or "4" I'd say go AF. You do however mention "same old lenses" so maybe you already have that covered (but then your answer would presumably be "1" or "4"....)