(This started life as a comment over at Suburban Guerrilla [1], when it occurred to me that it’s really a post.)
Update, Jan 22, 2012: At SCALE 10x [2], I had a chance to see a couple of the late, lamented HP Touchpads running WebOS. They’re beautiful! They don’t have the idiotic virtual keyboard described below. They respond to taps properly, even when done by me. HP are a bunch of idiots for cancelling that thing instead of just pricing it realistically.
An iPad started it, but this is really about tablets in general. I’ve been using computers since the 1970s, when we had to do stat programs on punch cards and use Job Control Language. I l-o-o-o-ve computers (although not those JCL mainframes, to be honest), and I’ve always jumped on each new thing as it came along. I’ve had to face the fact that I’m a gadget freak.
Except tablets. They seemed pointless. Portable TVs, basically. Mobile-type things like checking contacts, phoning, music, or web surfing I can do on my phone without needing a ten inch pocket to carry it. Then I had to use a tablet yesterday because my local hospital has gone all iPad for their check-in procedures. Twenty questions that would have taken seconds on paper took about five minutes.
The legendary touchscreen takes forever to respond to a tap. (I have very dry fingers.) I needed an “a.” Tap … tap, tap … tap, tap, tap, tap, mash whole top of finger down and hold. Get a “z.” Start over. Breathe on fingers so they have some moisture on them. Tap. Tap, tap, tap, — tap! Finally, an “a.” And so it went. If I had a tablet, I’d need to carry a sausage [3] to operate the stupid thing. 
But my shortcomings were only the beginning of the problems. I needed an “@.” Tap special characters key for different keyboard, get the one character, tap key for a-b-c keyboard, tap-tap-tap out a few letters, tap special characters key for different keyboard, tap out two numbers, tap key for a-b-c keyboard, etc., etc., etc. What a total and absolute pain. And this is what everyone is raving about? I’d get frustrated just entering a password, forget writing a message. The bitsy keyboard on my Nokia N900 is easier to use (and I am not good at using it).
The graphics are okay, so as a portable TV it would work except that you have to hold the thing all the time. Hold one hand behind your back while you use a computer to see how it feels to use a tablet, unless you’ve already trained yourself on the things. (Yes, I know you can get stands, but that’s a workaround, not good design to begin with.) And one more thing. You want the screen tilted up for visibility without neck contortions and you want the screen flattish for input without shoulder and arm contortions. That’s a problem.
I know there are lots of much more coordinated people than me out there. And also people with more normal skin. But, believe me, tablets are worse than useless for some of us.