The 85 1.8 is a great lens. As pointed out above, its negatives are a crappy MFD and its somewhat prone to CA at wide aperatures.
Since you already have the 50 1.8 another lens to consider is the 60mm macro. Its 2.8, not 1.8, but I use it often as a portrait lens and it does macro/close-ups. Its incredibly sharp and has nice bokeh. Its doesn't suffer from CA, like the 85 does. Also, 60mm is a nice FL on a 1.6 crop, IMO.