Looking at the tablet segment usually results in seeing two players; iOS and Android. Pretty much all tablets sold currently fall under these two platforms, although with so many making Android tablets you could make an argument that says they shouldn't all be lumped together for analytical purposes. You could also make a case for not including Amazon's Kindle Fire under the Android banner as it is nothing like other Android tablets, with its own separate ecosystem.
“We differentiate media tablets from tablets PC and windows 7 would fall under tablet PCs. We feel that media tablets are a different kind of tablet where not just form factor but the richness of the ecosystem of apps is part of the value proposition to users. Windows 7 was not an OS optimized for tablets.”
Tablet PCs haven't sold in what anyone would consider big numbers in the decade they have been on the market, but the fact companies still make them indicates they are selling some of them. Gartner seems to believe that doesn't matter because there are no apps for them and that Windows 7 is not "optimized for tablets".
That's a very distinct perception, especially considering that Gartner's numbers see Windows 8 tablets hitting the ground running when released later this year. They have "Microsoft tablets", presumably of the Windows 8 variety, selling almost five million units this year. That's a pretty healthy forecast considering Windows 8 won't likely be released until the last quarter of this year.
Windows 8 tablets will include both the Intel and the ARM versions, and apparently Gartner dumps both versions together in its numbers. They will technically run different versions of Windows 8, one relying totally on an app ecosystem as they defined it but the other not. It's going to get confusing trying to figure out what makes a tablet a tablet.
A tablet is pretty simple to me: a computer of any platform that has the ability to be operated as a slate by touch. That would include all Windows 7 Tablet PCs with a possible slate configuration and touch screen. The apps are totally separate from defining the genre in my book.