I'm in the same boat and believe my normal chair way of life is also dead.

I have tried many office style task chairs and none really 'solve' the problem of having to sit at a workstation for any significant length of time. I have the Herman Miller Embody chair (supposedly the Ferrari of all task chairs) and it offers no real comfort. The only way I can cope is to take very frequent breaks.

I wouldn't recommend a tablet if you have to do any serious work. The increased difficulty with touchscreen typing will probably cause more strain.

I'd like to hear if anyone has experience with a standing desk.