Tim Van Damme posted a fantastic mockup idea for the as-yet-merely-rumoured Tablet from Apple. His idea is that it can be used as a standalone device, but with an iMac-like and laptop-base-like base/dock stations. The former would provide a larger screen, graphics processing, and possibly extra memory and processing (don't forget peripheral and network connections!), and the latter would use the Tablet's screen, but could serve many of the same capabilities.
These ideas are very attractive to me. I currently don't think that I would get enough use out of a Tablet by itself, but this option could make it MUCH more useful and likely to me. If a company could pull this solution off well, it would be Apple.
This reminds me of a modern take on the Powerbook Duo line. I really liked that idea and implementation...