Yeah, I've got my own author site and have done lots of sales through it as well. I even design websites for other authors as well. But that's part of my day job (I do IT, Sysadmin and systems development work) and not connected with my actual website or my books. I actually find that by doing sites for others I learn more new and interesting ways to do mine better because others tend to think of numerous things I won't. So in a way it's sort of like having a brain trust, only your paid to be part of it.
Either way, in this modern highly connected digital world, an author site isn't "optional", it's required. It doesn't matter who does it, just so long as it's well designed, works right (ie, no errors) and looks good. It doesn't have to be uber fancy, but it does have to be both practical and functional. The easier it is to navigate, the more hits you'll get and the more potential readers.