I just noticed that CDN feature of W3 Total cache is not working as expected. I recall that it used to replace wp-content images with ones from CDN but now, it is not doing this.
For example, if you go to my homepage: http://bloggingwithsuccess.net/ and see source of first thumbnail, it is http://bloggingwithsuccess.net/wp-content/uploads/2010/12/Searching-Thumb.jpg while with CDN Activated, it should be http://cdn.bloggingwithsuccess.net/wp-content/uploads/2010/12/Searching-Thumb.jpg
This file is present at CDN, but plugin isn't using it. So basically, files are being uploaded and I am being charged for that but they aren't served, so no performance gains for me!