Being at home on a rainy day, but wanting to read some new novel that just came out, you can have it in seconds. This concept (not hobbled by DRM) is pretty damned liberating.
Granted the PDF converter seems to have some trouble with graphics PDF's, but for books the converter works very well.
The Kindle has many flaws, but it does allow you to read a few different non-DRM formats.
Ebook readers have extremely high contrast/readability and are extremely energy-efficient, being able to display several thousand pages of material without needing to recharge. eBooks are a narrow product, but they have their own ways in which PMPs cannot compete.