The effective focal length of the 85 is roughly 135mm on the 40D; the 17-40 and a 50 would be a nice range of focal lengths. The issue of focal length should also be combined with close focusing range on the 85 -- how close can you be to properly focus will determine whether or not you can use the the 85 indoors without backing up.
Here's some examples from the 40D and 85: the first is from about three feet; the second is from about 12 feet away; the third is a 100 perent crop of the first photo and not sharpened or put on a tripod...
here's some photos of the 40D and 85; the combo is pretty small, actually
click a thumbnail to see the photo full size
overall, I find the 85 f/1.8 to be a good buy and worth owning...
HTH,
Mary in SW Florida