For me, this will be one of the most important steps ever taken in the history of the GUI. Not just for those who are visually impaired, but will allow manufacturers to develop much higher resolution displays and graphics cards.
For me, HDTV is too low a resolution, UHDV is closer to what I think we should be working with. That will take many years, but should be a target and computers will lead the way forward for that. Imagine having your 20" iMac looking as crisp, if not crisper, as it does now, but with a higher resolution and the elements still remaining constant. The windows and text on the screen looking like they have been drawn onto the screen, rather than generated by a graphics chip, restricted by the size of the pixels.
I'll be hammering that point home, and I think that every store with Leopard on their display Macs should have windows etc all at the same size, irrespective of the screen size, to allow people to see that the resolution of a larger screen, (or same size comparing 17" iMac to 17" MBP), doesn't only mean you can see more on your screen, but for the same size window, it looks better.