I added a blog to my website about 2 months ago and it has been a great tool.
I get almost as many visitors entering my site through my blog as I do my home page.
However, the conversion of the blog visitors is much lower than those who enter via the main site but any traffic is good traffic. Also, even though the traffic is not as high of quality as far as potential there are those few each week who wouldn`t found my company otherwise and that makes it worth it.
I write a Family Travel blog and also blog on NHRA drag racing -- they both tie into my business as a freelance writer. My main author site is mostly to set up my bio, background and published clips on a more static site than the blogs.
You simply cannot be a high-impact author today without an online presence of some sort (plus, no editor fiddles with my writing on my blogs and I don`t have to wait for the magazine to come out!) :)