I think I made up my mind. I'm going to stop looking for lenses for the Nikon, for now, and save up more for a Canon 7D instead. Then later I may pick up a prime for my Nikon.
FWIW, it will meter fine. Any lens with 5 contacts will meter, but not AF with the lower end models... If you like Nikon and have money in lenses, you could always look at a D300, I just picked one up cheap and it is a great camera. Unless video is important to you the D300 is pretty awesome... just my humble opinion. The 7D is also a very good camera, but if you are on a budget, it might not make sense to have 2 camera systems....
I dunno if you read all the thread, but it makes sense in terms of availablility of lenses and gear. Instead of trying over time to save up for lenses and gear for Nikon, I can get a good canon body and be able to borrow and use many many things. I was looking at the 7D and 60D back and forth....and there is not a whole lot of difference....I would go with the 7D simply because once getting that I would not have to worry about an upgrade for quite some time as it will be more than capable of anything I want to do while I find my market area and learn where exactly I want to go.
I do still intend to get me a 85 1.8 for my Nikon. I have just changed direction in timing. The more I really thought of it, it just makes sense to me to invest in a body where I can learn and use many different lenses, vs invest in one or two lenses and be limited to those two lenses in the interim. I let myself get caught up in the excitement of having an awesome 85mm vs. thinking out what would make more sense in spending while learning.
I know Kundalini loves his and he knows a hell of alot more about photography than I do... But I was no fan of the 85 1.8 AF-D, the bokeh was just totally mediocre in my opinion and purple fringing was highly visable. The 85 1.8G AF-S seems to be superior.
After checking the manual for the D3100, I read it as being able to meter with AF-D lenses. I have used plain AF lenses with my D5100, which has a similar metering and AF system, and they will meter just fine but won't AF. http://www.nikonusa.com/pdf/manuals/kie88335f7869dfuejdl=-cww2/D3100_EN.pdf
All af lenses will meter with the entry level dslr's. AF and af-d require in body af motors. Only the afs ( I've read af-I as well but I've never seen an afi lens) will af on the bodies without af motors.. If you have a d40(x), d3000,d3100, d3200, d5000, d5100, and want to utilize the af function you need a afs lens. AIS lenses will mount but you need to manually focus them and won't meter( it doesnt take a rocket scientist to figure out though.) AIS will meter on the d7000 and any of the higher model dslr's but not af. These are old manual focus lenses from the manual slr's.
just go with the 1.8G you will be glad you did. I dont understand how you feel the build quality is better on the D, i would feel much safer in light rain or dusty conditions with a G lens and rubber seal than most D lenses. Why give up autofocusing? There is a post on here for manual focusing with a macro lens, well thats a macro lens, you pretty much have to manual focus, i have a nikkor 105micro when i shoot macro using that, i use manual focusing 100% of the time. Shooting macro is diffrent than regular everyday photography, you can just move back and forth. Why not to manual focus on D3100: -its not made for manual focusing -Tiny viewfinder -No split screen, only aid is the range finder, with a moving subject your subjuect will go out of focus faster than you can focus -Forget shooting wide open, DOF at 1.8 and 85 is REALLY small, trying to get something in focus with the viewfinder is gonna be an extreme challenge. -The lens itself isnt made for manual focusing Reasons to get the G lens: -Sharper wide open, less aberations, these two alone should be a show stopped -rounded aperature blades, better bokeh stopped down -Focuses with ALL nikon bodies i can see you getting the D lens for a camera with a built in motor to save some $$$ but for an entry level, just do yourself a favour and save the headache for something else. If you still want a manual focus lens then go with a TRUE manual focus lens, it will be a pleasure to focus, and it will teach you even more about learing to read histograms and such.
Any opinions I gave, such as better build quality on the older one, was from others' point of views...not my own. I have not even touched either so I can't say. Kinda why I was asking on here for opinions. Sorry if it came across as my opinion or fact. You put up some great points to consider, thanks for taking the time to post about it.