We finally got it back today. After spending an hour getting it rehung -- this thing never hangs easily -- including knocking over the ladder I was standing on once as I was getting off of it, we found that they had managed to somehow slide the shade from one end of the mounting bracket to the other, so there's a gap on one side and it rubs against the window frame all the way down on the other.
This, however, is not as bad as the fact that they've cut the strings too short, so that the shade will not go down the last three inches.
Gretchen is going to call the store tomorrow. I've suggested that she recommend a house call so they can see exactly how they've messed up.