Take a look at
Palm Addicts for coverage of the new Palm Foleo. It looks like a mini laptop, but it's a smartphone companion. 5hr battery life, instant on, and PalmOS on Linux. Seems to be aimed at MS Office documents and email and web browsing. Will eventually have more applications, and will work with more types of smartphones than just the PalmOS and WinMobile Treos.
It may have a while to go until is satisfies many users. Those that want a convenient form factor and reasonable price might be interested for email and document viewing or editing. But it's not a laptop or tablet pc replacement, so don't plan on doing heavy computing on it. Will it sell? I guess we'll find out over time.
Related: Palm Foleo - Will it be another step for e-books?