Unfolding Microsoft's Origami

H-P's absence is particularly noteworthy, given that it was one of the first vendors of both Tablet PCs and PocketPCs.

Representatives for both Dell and H-P declined to comment on whether they have UMPC devices in the works.

The lack of top-rank vendor support at launch "should be a concern," says Enderle. "You want as many people behind it [as possible]."

To be sure, few analysts are ready now to completely write off the UMPC. The small design of the devices could appeal to some on-the-go consumers, says Gartner's Baker.

And some analysts say it could be a big hit -- if it's done right. Unfortunately, outside of Apple, the PC industry has a history of having good ideas undermined by their complexity, says Enderle.

"This platform could be next big thing, depending on how good a job it does," he says. "If it were coming from Apple, that would be a lot more certain."