"Tog" still writes a column on human interface .. it's on the web now, of course.
Not surprisingly, WebMD's interface is clean, and easy to navigate. I've never seen what's inside the "paid" site, so I can't comment on what's hidden in there, but the public site is becoming more and more useful.
They now have made Scientific American Medicine available "for a limited time" to users of the WebMD site. To use SAM for free, log in to the WebMD physician's library page, click on the "Scientific American" button ... you should be able to find your way in from there.