I installed a GFCI in a bedroom a few years ago and added 3 prong receptacles down stream in that same room.
This weekend, I was painting another room, whose 2 prong receptacles are also downstream of the GFCI, so I decided to replace them also.
After reading this thread over the course of the last few days, I found this interesting, if not a little errie:
The neutral slot on all the receptacles was on the left. In order to just remove the old receptacles and install the 3 prong ones, without twisting any wires - just a simple in and out swap - all the grounds on the 3 prongers ended up - up!