>According to what I have read, it is pretty much the same as >the 1.8D optically.
In fact, the 85mm f/1.8D and 85mm f/1.8G are quite different in optical design.
The "G" version has 9 elements in 9 groups, the "D" has 6 in 6; the "G" is internal focus rather the the rear focus of the "D"; the "G" has 7 rounded diaphragm blades whilst the 9 blades of the "D" are not rounded.
Having said that, the performance of the two may well be similar. From my reading of tests (I've not used the newer lens myself), the "G" is a little better in some areas but the difference may not be enough to warrant making the change