While tablet PCs are accepted in increasing numbers by medical personnel, insurance adjusters and other vertical users, why haven't they gone mainstream?

Analysts cite at least eight reasons why tablets haven't done better, including their higher cost compared with standard laptops (up to $300 more), problems with touch technology and handwriting recognition software, and a shortage of suitable applications.

Recognizing those problems, tablet PC makers recently introduced new second- and third-generation devices in both the convertible and slate form factors. More new models are expected later this year running the Vista operating system, which will eliminate the separate Tablet PC Edition in Windows XP and the resulting inefficiencies, analysts said.

"Tablet PCs remain a niche product in the marketplace, used predominantly in vertical applications," said Leslie Fiering, an analyst at Gartner Inc. in a recent conference presentation. The tablet PC's "appeal to horizontal, mainstream users will continue to be minimal" because of higher costs, an "immature" touch interface and other factors, she added.

Fiering, who started following tablet PC trends at their introduction in 2002, makes the strongest condemnations of tablet PCs of five analysts interviewed for this story, but she also offers the greatest optimism.