I registered at Target and I had a great experience. I do not have a BRU or BBB near me so it was Target or Walmart and our Target has a great baby section (bigger than others I have seen). We did receive some duplicate items as a couple of our friends shopped on the same day and bought the same items off our registry (they even bought the same gift bags so they must think alike!). When i went to return them I had a gift receipt so it was no issue and I got store credit.
However we did get other duplicates and items we didn't want that we didn't have gift receipts for, so all i had to do was print a gift log from the registry machine and they returned it and gave me store credit. As long as it is listed as purchased on the gift log it doesn't count against that yearly max of $70 per person. I even got a bouncer that wasn't on my registry (i already had one so i didnt need it) so i added it, marked it as purchased and then went and returned it the next day using the purchase log without any issues. Their registry return policy is listed and it is clear, if it is on your purchase log you can get store credit without it counting against that $70 max/per person.