AFS 85mm f1.4G - awesome! Moved from 1.4D...
To be fair, if you are not particular and dont analyze your pics, apart from better contrast in the 1.4G - one will probably won't notice the difference between the 1.4G and 1.4D. However, if you really notice, especially at the corners the 1.4G is sharp at f2.8 and after. The corners of 1.4D will only get sharp after f8.0. 1.4G is weather sealed (if thats important to you...), 1.4D is not. The hood design in 1.4G is better - for putting on and removal, again if this is important to you...
What I think can be better in the 1.4G... in my view 1.4D seems to focus faster (? maybe my perception...).
So, it actually boils down to "if it is worth it" in your opinion. For me, I think it is.
A word of caution bros & sis', do test this lens on the spot with your camera when you buy. I had a bad sample that is not sharp wide open till f5.6. Subsequent one that was replaced is tack sharp all the way.