But that isn't true! I sent you a link to my test page, did you notice that alt text sits right on top of the image element when you turn images off in Firefox? And, that it takes on the styling of the <h> element naturally once images are turned off? You can't tell that there is text there but it is there and it is treated just as if it were regular text according to the specifications for the alt attribute.
You know, tedster is one of the most knowledgeable people around here when it comes to Google. I'm going to have to disagree with him on this one. My research shows otherwise.
Now, how do you test something of this nature?
P.S. phranque, why are you still overengineering this? ;)