I have not yet set up Aperture Vault specifically, but what I do instead is run a backup of everything in the "home" folder each day on an external LaCie firewire drive. As far as photographic images are concerned, when I have a CF card with images to be downloaded, I first download them into my Pictures folder, and then I download them again, this time into Aperture, so that I've got them in two separate places on the hard drive. I haven't yet burned any of those to DVD but I know I should start doing this as an additional protection for my digital images.
I have purchased a second external drive but haven't set that one up yet, and it will be specifically for my photographic images only. This is what I used to do with my PC and it worked out pretty well. With Aperture's Vault system, I think that I'll be able to protect and preserve my images even more effectively.