One of the main reasons we will never be able to be 100% accessible is that nothing stays the same. Companies update operating software, browsers get updated and so do the rules.
To stand a chance of being compliant you have to be constantly updating your site and sifting through what is good for the viewing experience and what is a distraction or unnecessary decoration.
PC or MAC the choice is yours.
Iphone, Android or Bada to mention a few mobile operating systems all offer solutions for accessibility.
So you can buy a PC and buy a copy of JAWS software from Freedom Scientific but for the same money you can by a Mac and never look back.