Most people don't read enough to benefit from a dedicated device. They'll likely find mobile devices sufficient for their uses.
However, it's the heavy readers and students who are most likely to really win with a dedicated device. Capture either of those two markets, and it is irrelevant if the e-reader goes "mainstream."
By the way, I love how the analyst who views women as the "new market" for ebooks apparently missed the whole "Oprah Kindle" thing.