Seriously, I have to think that the Oprah endorsement is critical. One of the reason people have been holding back is the same thing that kept people from buying Blu-Ray players--there are a lot of eBook Readers out there, and no one wants to commit to a device that will end up on the ashheap of history, leaving their eBook collection orphaned. That means waiting until one of the readers goes mass-market. If Oprah can marshall her legions in favor of the reader, that may put it over the edge in the format wars.
Update: Apparently, you get $50 off if you type in the promotional code OPRAHWINFREY