Your other points about Windows are conjecture and subjective, I won't argue against you.
The windows used on those so-called tablets is a desktop OS, designed for keyboard interaction and clunky if used with the pictured stylus. They still have a start menu for example. That is not a subjective point or conjecture.
I still wouldn't buy a HP tablet because I would never use it in tablet mode.
The HP 'tablet' is just a laptop with swivelling screen, it's really in a very different class, and any purported slate will not be targeted at people who want a full keyboard, swivelling screen, etc etc. If you want a keyboard, why not just buy a laptop? That's fine, but there is a market for lightweight touchscreen slates which can be used for consuming media, which is a superset of the market for slates which can be used for reading books (e.g. kindle etc).
What is exciting about a new slate from Apple is precisely the factor that you seem to be ignoring here - the software that will come with it (presumably based on iPhone OS) could be a radical improvement from the present unconvincing slate offerings. Comparing it to tablets running Windows and using a keyboard and stylus combo for input is missing that point. It doesn't have to be a first to market to be far better than all the others, but of course we'll have to wait and see what they offer before any judgements can be made on that point.
However, the bolded part is just false and FUD.
My mistake, based on previous Nokia offerings. Didn't know they had a full Mozilla browser on offer now, as I've only seen friend's devices. Not so much FUD as uninformed; thanks for the correction. Not sure what the browser UI is like, but presumably they have gestures and pinch or double tap to zoom etc too?
I would note that the N810 is a tiny device, and is more in the range of the iPod or a phone rather than any slate. The screen is only slightly bigger than the iPod touch, and thus it would be a similar experience to that rather than anything to compare with a slate/tablet. Apple won't be the first to ship any sort of touchscreen tablet, but they might be the first to get it right. All the offerings you have listed so far are really quite unconvincing for various reasons (at least for me, your mileage may vary), and are not directly comparable to a slate format in many ways (too big, too small, desktop software etc). Those windows attempts are a kludge which keep all the disadvantages of laptops, and the other stuff from Nokia is close to smartphones or music players.
The tablet market does not exist as yet as a separate market. Those areas which do come close to a tablet (like smartphones, iPods or ebook readers) are booming and just about to expand massively.
Soon we won't have any physical CDs, DVDs, books, magazines, newspapers. In some of those sectors the transition has already begun (music, newspapers), in others it's just starting (books), and all that content needs killer devices to consume it on. That's where Apple comes in.