Pre-installed Linux must play commercial DVDs
You probably know this, but a "show stopper" requirement for most consumers and many educators and business road warriers is having laptops and desktops that can play commmercial DVDs. I have a hunch that preinstalled Linux on Dell machines will be a terrific success if Dell Linux desktops and laptops have this capability. I've been told that http://www.videolan.org/ has one possible approach.
Having Linux playing commercial DVDs may also catapult Dell into the complex Digital Rights Management contoversy so it would be wise to get Dell's legal staff involved ASAP and also have this discussed this at the highest strategic management levels at Dell (if this is not already being done).
Check out the Ideas in Action post from Daniel Judd. And you can also check out this follow-up post from John Hull who leads our engineering efforts behind Linux on consumer systems.