I have always been of the opinion that you should buy something they registered for. Even if it is boring for you, it's stuff the want, and most likely NEED. Most the gifts I received that were not on my registry I have never used, or have gotten rid of. My great aunt went out of her way to get these expensive hand painted wine glasses she thought were fantastic. We'll they don't go with anything of mine, and I don't drink wine. Even though it was a nice thought, it was a waste.
My friends also just had a baby. They hardly got anything from their registry. Everyone bought cute baby things. As nice as those things were, they didn't have the things they needed. You should have seen how excited they were when we gave them a bottle set. They were thrilled!
So unless you know the gift is something they'll love, I think you should get something off the registry. That is for sure something they will really like!