I was asking myself the same questions as you were when I began looking into a website. I think Gayla touched on what made me focus more on my site. When I googled my name, I was not first on the list. In three days I focused my site to make sure when you type my name, my site is first.
It was quick to move up because not much competition for it on google. But think of what all people search for in real estate, and try to be first on the non-conventional searches, and you'll see much better results.
Plus, don't spend too much money on your site. With all the site builder software out that is free, I only spent $124 for the year and that included the domain name. I have the space to keep about 20 listings on there. I use links back to my broke site for more properties which reads the cookie showing it was from my site and I get the lead. Was well worth the investment. Also, most of the software make SEO much easier to obtain.