The Kindle has many flaws, but it does allow you to read a few different non-DRM formats.
Plenty of free e-books in Mobipocket format show up fine on Kindle.
Typically ebook readers are larger than PMP's with larger screens. If you're going to read for a few hours, then the screen of a typical PMP becomes pretty eye-straining (due to size, contrast, and brightness).
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.
A revolutionary portable reader that wirelessly downloads books, newspapers, magazines and blogs to a crisp, high-resolution electronic paper display that looks and reads like real paper, even in bright sunlight.