6. Tablet PC software for pen-enabled and touch applications has not been widespread, nor has it always been effective, until recently.

"The good news is that support for most key vertical industries and from major ERP vendors now supports tablet PC clients," Fiering said. Recently, more form application-creation tools have appeared. However, some typical PC applications, such as Adobe Systems Inc.'s Photoshop, don't fully integrate pen input, she noted.

7. Vendors of tablet PCs have largely failed to market the devices to consumers, focusing instead on vertical markets within the business segment.

"If vendors went after consumers, it would help" sales, Shim said. The value of touch screens, as an intuitive technology, needs to be marketed to consumers as well as mainstream business users, he said. Mininotebooks, such as the OQO, could be marketed to consumers who are also business professionals, possibly expanding the consumer base for tablet PCs.

8. Perceptions that tablet PCs have not done well in the market make it harder to persuade buyers to try them.

"There's a negative stigma about tablet PCs now. People think that once they've failed, they are a failure forever, and that's not necessarily the case," Shim said. "It's true that they haven't lived up to expectations, but that's not everything."

Microsoft was asked why its tablet PC has not reached the mainstream as hoped for five years ago, but a representative did not answer directly. Instead, the representative issued the following statement via e-mail:

"As users seek the benefits of mobile computing, Microsoft is enhancing mobile features for all notebook PCs, and Tablet PC functionality plays a key role in this vision. In particular, the Tablet PC gives users the flexibility to use multiple forms of input to interact with their PC in more natural ways and get more things done from more places than ever before. As the Tablet PC platform continues to grow, Microsoft expects to see Tablet PC functionality on all Windows mobile PCs."

Meanwhile, plenty of success stories are starting to appear, and Fiering said she has seen growing interest. "Tablet PCs have followed the typical Gartner hype cycle around new technologies, which means they go through a frenzy when first introduced to a trough of disillusionment" and, usually, a gradual upward climb, she said. "But they are still growing steadily."

Fiering said she used to hear of sales of tens of machines and then hundreds, such as nearly 500 Fujitsu LifeBook T4000 tablet PCs that are being used with campus Wi-Fi at St. Clare's Hospital in Wisconsin, to collect, share and store patient data. Today, Fiering said, she is hearing of tablet PC orders by businesses topping 5,000 machines.

Even with such optimism, Fiering admitted there's a nagging question whether the tablet PC can become mainstream, and she counsels her clients about it. "I actually talk large business accounts out of buying tablets across the board, but if there's a particular problem to be solved with a particular work group, they're fine," she said.