I think so, yes. AW can go down, if nothing else. Best of all I can say exactly what I want to say, and if you add reciprocal banners you can get free listings on some other sites.
Also, when I get a generic text enquiry, I always put the URL in my response (keep it short and snappy!)
Finally, anyone can create an AW profile or a VivaStreet ad in a few minutes - I think having your own website adds a bit of reassurance that you're a professional.