Excellent idea and very nice execution! The design is great, plus it's incredibly easy to signup and share your registry. You're definitely on to something here.

In terms of suggestions, I'd suggest you tweak your index page a bit. When I landed there, I was most interested in seeing what one of these registries looked like. I assumed that clicking the image of John and Jane's Baby List would show me an example, but it's not currently linked. To actually find an example, you have to think a bit and either find the text link under your Create button or realize that the Showcase link is what you're looking for.

Also, the Vendors page needs a bit of work. I'm sure that's number 7273 on your priority list, but I don't think it'll be very successful in engaging vendors as is.