deadsea - 11:47 pm on Sep 13, 2011 (gmt 0)
How are you measuring that traffic drop, via client side monitoring (Google Analytics) or server side logging? If you are looking at your server logs, I would expect you to have less traffic, that is what CDN is for, it serves the traffic so that you don't have to.
Using CDN for www pages is not a common practice because it precludes customization for each user. If you content is static enough that a CDN will work for you, then I'd imagine it helps user experience by having the page served faster which should help SEO. I certainly don't have any first hand experience with such a set up though.