I registerd at Buy Buy Baby and Babies R Us and had overall decent experiences with both - was able to modify my registries online and was able to return items to both stores with no issues. I did have a few random issues with BRU - none of which were huge deals but still very annoying:
1) after registering in store at BRU, I went home and looked at my registry online and saw some items I did not register for, as well as some of the wrong colors for items. While I could delete the items I did not register for, I could never change the colors on the affected items.
2) I thought some the descriptions on BRU registry were hard to figure out especially on the few clothing items I picked.
3) they put on the registry that I wanted batteries and the protection plan for certain items, which I specifically checked I did not want when filling out the form. I could never change that online so I just included a note at the top of my registry saying to ignore that.
If I could have, I would have registered at BBB only but it was not geographically convenient to most of my shower guests.