How comparable the reading experience is between paper and the Kindle is probably a gray area (pun intended). Certainly some mass-market paperbacks have poor print quality and poor contrast, and yet people buy them. The displays are reflective, like paper, (not emissive, like LCD screens) so they should be easier on the eyes. And one can reasonably expect that the quality of displays on these devices will improve incrementally over time.

The problem with the Kindle is its emphasis (by design) on being book-like. Although it is a computer, it is designed to hide that fact from the user as much as possible. This drives in part the need to have a long battery life (who wants to charge a book just to read it?), a low-power (hence bi-stable, hence monochrome) display, and a low-power CPU. The less powerful the CPU, the longer the battery lasts.

So in the end, you get a reasonable book-like reading experience, with a nearly invisible computer. But a side effect of this design choice is that the computer is unable to do anything else that it might otherwise be able to do to help the person read more effectively and efficiently. Reading aids such as search, juxtopposition, annotation, translation, animation, etc. are discarded in favor of long battery life.

This is great for reading novels, but not so good for other kinds of reading that many people do professionally.
As John pointed out in his comment above, words-on-paper technology has evolved to meet the demands of readers. I hope that e-book technology will evolve to support the entire ecology of activities that accompany reading, rather than declaring victory and withdrawing.

I can't tell from your article if the makers themselves claim that their new gizmos will actually encourage reading in any way, of either short-form items or traditional, bookish texts. If they do make such claims, then it's worth asking that they prove those claims somehow. Jon Stewart's statement may not be cause, however.
I suppose the makers' response might be that the proof is in the pudding - that strong sales of their machines, especially sales beyond the I'll-buy-anything "early-adopter" crowd is done with its purchases, would show that this new way of reading is worthy and useful and perhaps more attractive than using traditional books.

The suppliers might also respond by asking why they should be required to prove anything about their products. That's just not the way things work, is it?, in this free-for-all marketplace of rampaging digital technology, aka today's world. Is Facebook required to show that its (hugely popular) "social networking" service somehow improves friendships, however one might wish to measure that? Is Google required to prove that it's NOT making us dumber, as some journalist-critics have suggested (I have not actually read N. Carr's Atlantic Monthly article that was titled to this effect, last year, but like many people, I find the question he raised most intriguing.)

Apple Computer surely seems to have succeeded, with its iPod/iTunes scheme, in essentially dismissing and obsoleting the decades of effort that the hi-fi industry put into getting us all to buy ever-more spiffy home stereo systems with which to listen to our ever-expanding collections of recorded music. There's no question about the inferiority in the quality of sound available from digitally compressed audio files (MP3, AAC, etc.) versus well-made optical or vinyl disks or good audio tapes, etc., played through good speakers, etc. Yet, even with its comparatively inferior sound quality, the iPod and similar devices have enjoyed massive acceptance, evidently because they provide sound quality that is good enough along with the added benefits of greater portability and less need for messy, space-consuming stacks of records, CDs, and cassettes. (The iPod also does away with the album cover and CD booklet, which I, like many old people (!), tend to miss.) And neither Apple or any other maker of portable audio players is expected to show proof that its wares improve listening habits or make the world better or increase the public's general understanding or appreciation of music. They put a new type of product on the market that has, for whatever reasons, and with whatever side-effects, has succeeded. The market has spoken, in other words, so what more is there to say?

Now, that attitude or response - the market knows all, technology proceeds, shut up and take what it gives you - is clearly open to criticism. And the more I think about the digital juggernaut, the more I wish I were hearing more such criticism. Perhaps resistance is futile, but one only has to look at what the automobile has done to the geographical landscape of America (and increasingly, that of the entire world) to wonder what the Internet (including Kindle, etc.) is doing to our mental landscape and human habits.

Perhaps Kindle et al will change book buying and reading habits in a similar way. It will be interesting to watch. Already, so much reading - consumption of text? browsing? surfing? what's the right verb? - has moved from the paper book and magazine and newspaper to the digital screen connected to a seemingly fathomless reservoir of "content." And we should remember that reading as we know and think about it - from bound sheaves of paper, silently to ourselves, etc. - is not a given; the act of reading has changed radically during the course of history.
Until the Middle Ages, reading (in the West, at least) was mainly a vocal exercise, performed either out loud to a room full of fellow scribes (hence the word dictator) or as a quiet mumble to one's self. The words monks read from scrolls and books were generally considered to be the words of God, each one a succulent morsel of sweet wisdom to be savored and voiced. In fact, for centuries, words were written without a space between each one, so only by reading aloud could a text be read and understood. Eventually, words got separated by spaces, and alphabetized lists of topics, tables of contents, indices, footnotes, and many other new structures were employed, and the text was disengaged from the page - virtualized, one might say, and made available for silent contemplation. And much more, much of which is artfully described and analyzed by Ivan Illich in his 1993 book, In the Vineyard of the Text.