I grew up in a very diverse community, from an ability perspective, so I am used to being around highly functional and productive paraplegic, quadriplegic, blind and/or deaf people.  This means that in discussions about Section 508, the section of the Americans with Disabilities Act (or Americans with Dignity Act) that deals with software and websites, I have a certain bias. 
 
I know people can and want to be active society members regardless of their physical abilities.  I have also lived and travelled in other countries that don't have the ADA.  The ADA is one of my favorite American acts of optimism through government.  It puts potential first, leveling the playing field in a way that most other countries don't dare to do.   The result, in my experience, is a richer community of American dreamers to pull from.  But people who don't have personal experience with these issues often don't see the value in putting adaptive measures in place.  And so I have had many a fight over Section 508 compliance and its value.
 
After more than a decade of battling over this, I am delighted when something comes along that proves several of my points:
 
1.  Adaptive design is good design.  CNet has an article on Reader's favorite uses for the iPad, and many of them boil down to adaptive attributes: portable, light, easy to read, good movement tracking.  It wasn't extra work to create these features, it was part of creating a well-designed tool for everyone who might use it.
 
2. Adaptive design can lead the way.  Many new design and technology ideas are tried first in adaptive designs, and then taken mainstream - including the iPad.  See the great blog "Eat quads' dust, iPad users"
 
3. Adaptive design is flexible.  It is simple enough that it can be modified and tweaked to work in a variety of circumstances.  This video shows a designer using his iPad instead of a trackball. In 5 minutes, he is more accurate than with the trackball he's had for 6 years. Trackball comparison

4.  Adaptive design is powerful and empowering.  The simplest application, designed with the right users in mind, can change their entire world.  See this thread about a mother trying to communicate with her stroke-bound son.  All she needs is an iPad application that lets him say Yes or No.  And she's not alone, the application was already created for another boy with communication challenges. 
 
See AtMac.org for more about iPad's possibilities.  And don't be afraid of designing with these audiences in mind.  You will find that designs which are good for 'them' are good for the rest of us, in at least 479 ways . . .