I would HOPE the new ATV is better clocked than the AirportExpress. My DAC, a CA840c simply doesn't like the AE with its huge jitter.
Also, the ATV is only 720p, not full 1080, I or P.....which means that full pixel displays will have to do the conversion to a 1080 line display.
No memory in the new one, either? Can you hook up a HD for storage or system backup?
As near as I can tell, the new ATV is merely a video AirportExpress.