Hi
To save people who are thinking of buying a Kindle DX who have eye sight issues I have placed a few comments below for you to bear in mind if you are thinking of purchasing this device in it's current incarnation.
(1) Font sizes are limited at present there are 6 but for people with sight issues I would suggest that all but the last maybe 3 are of any use to them. For example the 3rd and second last sizes go from approx 44 to 22 characters per line which is a big jump and also means more presses on the next page key . . . ( the above assumes you have chosen the full width option for text because the Kindle does have a useless option to narrow the page which adds wider margins and centers the text and thus gives you less characters per line and on a page . . . go figure.
(2) Fonts, styles or sizes are not available so you are stuck with what ever the publisher choose for the book so its best to get a sample the book first before you buy it because if you don't you maybe stuck with a book with a very fine print and a font that is hard to read . . .
(3) The text sizing is NOT available on the main home page or the shop page and even when reading a book, the search and other functions are in very fine small print which you can't change. So basically you are stuck with the size print then has selected. Thus I buy on my computer, and always keep a magnifying glass handy for other issues . . .which is something i should not need to do.
(4) The Kindle key board from hell

. I have the DX graphite version and the keys have a silverish print on them which makes it hard to read the small keys but i assume Kindle was probably more worried about looks than ability to read clearly. Also the key are VERY small with even small print . . .
(5) The screen is not back-lit so in good light its is fine to read in but in low light and in bed ( night ) you will need to have a lamp on or a book light. You will also need to ensure that that the light is angled so it does not reflect back in the screen you are trying to read . . . I think back or edge lighting would be better here . .
I purchased a kindle because the iPad being first gen had issues and at the Australia price, which is much dearer than the US one, I decided to wait and see what version 2 brings. The Nook by B&N and Sony were my next choice but neither sell or are supported outside the US unless you buy from eBay or the like and have no support and no access in Sony's case to their book store. Thus the Kindle, Amazon at least sells and supports Australian buyers and sells at the same US price you only need to factor in the currency conversion rate.
I have for sometime now been unable to read normal books which is something I have done, and enjoyed, All my life . . . i rather read a good book than watch a movie . . . So I went to audio and ebooks . . . to date i have been reading ebooks on my computer but wanted more freedom so purchased the Kindle . . . I wont go into the issues of not being able to buy books both audio and ebook because I don't live in the US . . . that's another frustrating topic for example i can always (subject to certification) paperback or hard cover book which i cant read and sometimes the audio but not the ebook, sometimes the reverse some times neither ebook or audio . . .go figure . . .publisher greed . .
I will update this post as i learn more about the device I now own . . . At present it appears to be a very basic device . . .
I am still getting use to the pages blacking out as they turn . . .
What can Kindle developers do to fix some of the above . . .
(a) Add font style, size and types and drop the text size basic format they have chosen or add for sizes and ensure all kindle books are sold with a decent stand font before they are added to the store.
(b) Add a touch screen and loose most of the buttons and keyboard . . . as per Apples iPad/iPhone/iPods
(c) If they still want to use ink screens then add edge lighting to the screen . . .
(d) Add memory card support especially since they can play audio and music files as the current just under 4G will soon run out once these files get installed in the current versions
Just a few ideas that leap to mind . . .
Please note the above is just my slant on the Kindle I suggest if possible you try and get some hands on with one before you buy e.g. from a friend and try and read other reviews and comments preferably not on the Amazon site.
One last Comment
The Kindle DX is not a light device I find that in bed I now use a pillow behind it to help support it and another under my arm to support it as holding it up high enough to hit the next button causes issues with my arms hands and wrist ( bear in mind I have health issues so this may not be a problem with any one else)
Hope the above is of some help to some one . . .
Thank you for taking the time to read this post