With revival of rumors of an Apple's Set Top Box, it's interesting to see direction of the rest of the industry. Microsoft released information on Mira in Jan.
Unlike many other Web tablets, Mira actually doesn't function as an independent computer. Instead, it effectively relays data and commands back and forth from a PC via an 802.11 wireless network and Windows CE.Net, the latest version of CE. Letting the PC do most of the heavy lifting saves on battery life.
With an expected cost of $500-$800, I'm not sure how successful they will become... especially when laptops can be had for not much more.