I rarely shoot the 105 2.5 stopped down but about 2 months ago I was shooting it @ f/8 and IMMEDIATELY upon inspection of the negs I went...woah...(this thing kicks some serious behind)

Now I've only used the 85 f/2 and that was when I borrowed one on a large project I was assisting.

The 85 1.8 gets tons o luv and also gives you a good deal more handholdable speeds in low light.