That's OK, I'm sure when you delightfully correct people about this oversight, you don't skim over things like the Newton or the Palm Pilot, or the prop from 2001 that was hugely inspirational, and that you go into great detail about all the technical and usability differences between iPads and early-2000s tablet PCs. I'm sure you give fair and equal coverage to all of these topics when you are correcting people, since you seem to care about history and stuff. Just giving you the benefit of the doubt here.
I bought a Compaq TC1000 when I graduated highschool for $750~. It was one of the very first "Tablet" PCs. It received a LOT of very positive attention when I used it on campus in college. It was a great machine and was very usable even with limited OS support.
Microsoft had a marketing problem (they still do) and not a usability problem.
