The marketing mistakes per Microsoft in terms of Tablet could fill a book (I was there I saw all the drops and the missed opportunities) but even so, the real culprit was a lack of any sort of compelling need, outside of difficult to integrate verticals and some gimmickery Educational apps.

NEC? Whatever. No one took them seriously anyways, more a please-Bill-Gates-prototype. The Motion and HP Slates got all the attention, until pure Slates bubbled-out and everything went convertible. NEC was thin and light, but that was it, battery life was in real world use around 45 mins, 2 hours was not doing squat with it, off WiFi. And the stupid Wifi attenuator was weak and broke off all the time. I really wanted to like the NEC, but obvious it wasn't any more real than Dukakis was a candidate. So no matter all your newsgrouping and trade show harping, no biggies even bothered a look. The richie Redmondites and curiously insane early-adopters were the only ones that showed any interest.

The Problems…

1. Poor Ink integration, Windows 7 fared better, but it's still not a pleasant environment, and XP and Vista were trainwrecks. Office is still an Ink no-man's-land.
2. Price, Resolution and over-expensive Vertical market third party software mainly.
3. They abandonwared MS Reader and and sort of eReadering, too early, too expensive, way too DRMish, Steve Stone stubbornness de jour.
4. The typical insular inside-baseball MVP Microsoft community mode, Pocket PC redux.
5. OEMs pushed all to Microsoft, Mircosoft pushed all back. Nothing ever got done. Even a simple lunch at CES was an earth-moving task requiring the Heinys to go 24/7 for weeks.
6. 11 Agency retail trade tours and etc. were horridly handled. Trainwrecks wouldn't even cover it.
7. Bill Gates dream hard-sell had skeptics everywhere. Marched in like it would set the world on fire, instead of letting it bubble-up. Press blowback was monumental. Apple does hype in reverse, which tends to succeed more, but then kills the markets by not letting OEMs in, and being cultic expensive.
8. No touch. In spite of all the active digitizer talking points, people still wanted to touch it. Microsoft later reversed course, about when everyone had quit paying attention.
8. Third parties looked, sniffed and avoided. And most became gee-whiz Educational tricks.

Microsoft really can't market to consumers, never have, never will. And where they “succeed” they have to waste 8 billion or more to get there. Count them up….Zune, Wifi hardware, SPOT watches, WebTV, Ultimate TV/MSN TV, eReaders, Tablets, Origami, Phones, PDA/WM/CE, Red Ring of Death. Mouse and Keyboards for awhile, but even that bright spot hovers and dips.