If you want to do more than web browsing or gaming you need to seat down and put the computer on a flat surface. I don't see how it's possible for people to easily work while holding the device or leaning it on something.
If you're talking about the iPad and not a laptop, from what I've seen it's actually preferable to hold it in one hand for a number of work related tasks.
I encounter this scenario almost daily at work I'm away from my office, need to collect data for later transfer to a spreadsheet or a database, and would never consider using a laptop to do this.
In addition to lugging the laptop around, waiting for it to boot up or resume from standby, navigating and launching the correct program, I'd also have to do this while balancing the thing in one hand. Entering data into a spreadsheet while balancing a laptop in one hand is not the ideal situation.
So what I do instead is use a notepad for this task, which I can in fact use with one hand holding it. An iPad would be similar to this- Better in fact for two reasons. First, the keyboard is context sensitive. And second because I don't have to transcribe the data in my office back into the computer. It's also better then a laptop for this task because, as has been previously observed, it''s an instant on device that is easy to navigate with a touch interface and rapidly launches compact applications.
I can envision other work related tasks where the iPad will likely prove superior to a laptop, based primarily on the advantage of the form factor in mobile situations over laptops.