I got a HP TouchSmart TX2Z tablet a few weeks ago. So far I love it. I've got Win7 on it and it's been great. The past week or so the keyboard has simply been useless – doesn't even work at startup to get into the BIOS. I took the thing apart thinking perhaps it was unseated – was seated fine. I discovered some obscure comment on a blog saying that someone else had the same problem and they had remove the battery (and AC power) and then put it back in and things were fine again. I did this and sure enough the tablet keyboard works again. Got me what's wrong with it but this solution is surely better than having to try and explain this situation to HP's consumer tech support in Bangalore or Chennai.
UPDATE: Apparently I was 9 revisions behind on my BIOS/firmware. The release notes for the current rev (F.12) mention fixing an issue with the keyboard not working. Hopefully this will take care of it.