MacRumors notes that the HTML5 version of the videos doesn't work yet, but there does seem to be full screen support and the CSS fills reference HTML5 and have a number of specific "webkit" calls.
Many, including Steve Jobs, see HTML5 as the successor to Flash -- and things aren't looking too hot for the Adobe plugin's continued dominance. In January Google launched a HTML5 Youtube beta site followed by Virgin America announcing earlier this month that they dumped Flash from their website because the iPhone doesn't support it. Of course, HTML5/iPad support doesn't mean CBS is ditching Flash. They could be following in the footsteps of NPR and the Wall Street Journal and creating two different websites -- one Flash-free -- for users of the iPad. Whatever the case, it's nice to see CBS planning for the iPad and one hopes the other major networks will follow suit.