Tablets existed LONG before Apple. They even ran Windows. Post-iPAD tablets are released all the time. You want rugged? Its there. You want built-in bar code scanners? There. Digitizers instead of touch? Yup, you can get them. Digitizers AND touch? EEE has one coming.
Win7 runs like a champ on them, especially if they are pen and not touch based. Touch works, but nevermind that touch-based PCs have been around for ages (HP sells a lot of them), not many app vendors actually try their apps on them. Complain to your app vendors if you don't like how their apps behave on them.
Problem: people didn't know how they wanted apps to behave on tablet form factors until Apple showed them.
And it's not that there's anything magical about Apple, it's that that they did the work of figuring out the best approaches for the form factor and working out all the details--work that anyone else could have done but that no one else actually did. Microsoft tried--admirably!--but stopped short, putting crutches on an interface designed for keyboards and traditional pointing devices.
Look, there's presumably some reason people want iPads but didn't want Windows XP Tablet Edition. It's not users' faults for failing to unlock the potential of the tablet form factor. It wasn't our job! Apple pulled some M. Night Shyamalan shit with the iPad; nobody thought of it themselves, but after it was revealed, it was obvious. Now everybody takes it for granted how obvious it is and comes up with really cynical reasons why nobody saw it before.