I’m not going to predict how well it will even perform under one handed operation, however even if it were only as light as the average magazine (like say Communications of the ACM, which I have here on my desk), holding it up with one hand and operating it with the other is going to be a strain even if the arm holding the ipad is supported.

Damn, I think I just talked myself out of buying one… maybe

Personally I’m really quite excited about the iPad and it might well be the first Apple product that I have bought in something like 6 years -  but I’ve had a niggle since I first saw it in action and read about it, which I haven’t seen anyone else pick up on yet (SURELY someone will). That is how inherently awkward double handed interactions with large portable interfaces (or tablet PCs) are.

“What?” you say…

This, I say: that in order to use two handed interactions, you need to put the iPad down on something - sometimes rather suddenly mid interaction - and that to do so is just plain ergonomically unsound.

Let’s review some options for using the iPad:

1. Your lap

Some may remember the days of the NTL set top box and its walled garden internet when internet through the TV was trialled 10 or so years ago. Some clients rushed to get their websites converted for the walled garden so that they’d work on the TV. You had to use certain colours, no stripes, I think it was 640 x 480 resolution, HTML 3 (no frames), table based layouts only, and absolutely no javascript. To interface with this wonderful garden of delights you used a keyboard on your lap.

I didn’t need to conduct any usability trials to work out how this would go. Try it now, put your keyboard on your lap and see how comfy it is to use. It isn’t is it?

To see this in action check this video about how to use an Apple application at 20 – 35 seconds. The narration suggests it's easy but watch what the narrator actually does with the tablet.

2. A desk

Place the iPad on a desk and suddenly you’re craning over at an 80% angle to look at the screen (which is normally upright) in order to see what you’re doing. "Ouch, my neck!"

3. A stand / mount

With the iPad on a stand here are your choices: either the keyboard is at the wrong angle, or the screen is, or the whole thing is at the wrong height, or more likely all three… That's an Ergonomics fail!

4. Your lap II

Legs up on your sofa, knees raised, head rested on a comfy cushion, iPad on your lap. AHA! The one comfortable position in which you can make your double handed interactions; just don’t forget some Velcro to stick your iPad to your trousers to keep it at just the right position.

But wait, OH NO, now my wrists are at a 90 degree angle to my arms. "Ouch, ouch, ouchety-ouch."

In conclusion, the ergonomics of the iPad is not looking good. I’m not going to predict how well it will even perform under one handed operation. Even if it were only as light as the average magazine, holding it up with one hand and operating it with the other is going to be a strain even if the arm holding the iPad is supported.

Damn, I may have just talked myself out of buying one… maybe...