We had four registries: one on Amazon.com, one at Target, one at Bed Bath & Beyond, and one at Home Depot. This page summarizes our experience with each of them.
For guests willing to order online, the Amazon registry was perfect. It has a "universal registry" feature which allows you to add any item available online, not just items on Amazon, to your registry. Thus, we were able to consolidate everything we wanted from any store on it. Guests could look it up using either of our names. The only real down side of an Amazon registry is that it doesn't work for your computer-phobic friends.
This was the most user-friendly registry of any of the brick and mortar stores. We went in and set it up, then used a scanner gun to add items we wanted. However, we were then able to modify it either in the store or online. Guests could access it online or in the physical store, using either of our names. And BBB's policy is that you can return any item on your registry for cash, without needing a receipt.
Target, like BBB, allows for the set-up and modification of the registry either in-store or online. In-store, items can be added using a scanner gun. And guests could locate it in-store or online using either of our names. The one issue with a Target registry is that Target seriously limits the number of items you can return without at least a gift receipt. Fortunately, all of our guests followed our instructions on including a gift receipt with the gift, so this did not pose a problem for us.
The Home Depot registry was terrible! First, we actually had to go into the store to set up the registry; we couldn't set it up online. To add things to it, we had to walk around and write down the bar code numbers, as there was no scanner gun. Even once the registry was set up, it could be only used in the physical stores, not online. To use it, a guest had to know a registration number we were given, as there was no way to look it up by our names. They also had to know the store number at which we set it up. Every guest who tried to use the Home Depot registry ended up just buying us a gift card for Home Depot.