Up until this point I've been using various programs on my various models of Palm PDAs. Mobi Reader, Plucker and eReader were the three I used, mostly I settled on Mobi. Which is convenient because I can read all of my unprotected Mobi books on the Kindle since that is the format it uses. On the other hand I have books that are DRMed that I can't read and tho the ebook retailer will let me register multiple devices so far I have not been able to get them to work with the Kindle.
I'm ready to leave those books behind for now tho. The Kindle is a much nicer e-book experience. First and foremost is the display, e-ink displays are so much nicer to read for long periods than and LCD. I have to use a book light to read in the dark like a regular book since e-ink doesn't do back light. Mostly this is ok, but I think they could have built in a pretty simple low power LED light solution for night reading. Now of course this display is the same type of display used on the Sony e-book and the iRex Iliad. It is also the exact same display as the one on the upcoming Foxit eSlick reader, which looks like it will have way better PDF support and will be cheaper than the Kindle. I'm still betting on the Kindle experience.
I've made my way thru six books, a couple articles and a short story. I'm a little over halfway thru my seventh book (David Weber's - The Short Victorious War), and I have several other novels all loaded up and ready to go. I have a full copy of the Bible, the Dao De Jing and a pretty good cook book from Cooks Illustrated (this was a free book from Amazon).
The Kindle comes with The New Oxford American Dictionary installed as it's built in dictionary, new dictionaries can be added but this has worked great so far. Unless they release a copy of the OED for the Kindle I doubt I would bother with another one. Using the dictionary is really simple while reading, just move your cursor in front of the word you want to look up and a two line definition pops up at the bottom of the screen, and if you want a long definition you can hit enter and it will take you to the full entry. Once you are done, just hit the back button to return to where you left off.
I love the Whispernet (Amazon's always on cellular Internet connection via Sprint) and the ability to easily look things up on Wikipedia or Google when the dictionary just isn't enough. Of course the whole reason Amazon is footing the bill on this is so that you will use it to buy books from them. The Kindle store is easy to search and use. Once you buy a book it really does download in seconds. They have over 250,000 books available and this will only grow over time. One thing I like that they have added to the normal Amazon store is a link on every book that does not have a Kindle version that says "The the Publisher! I'd like to read this book on the Kindle." This is great because hopefully Amazon while have enough weight to push more publishers to put out e-book versions of their books. Because there are some big holes in the e-book library. Like for instance, all the Harry Potter books. J.K. didn't want them released as e-books because she was worried about piracy. I've got news for her, I downloaded an e-book version of the last several of her books less 24 hours after they were released, and I only found maybe a half dozen typos in three books. (I also had the dead tree versions to compare, but it was way more convenient to carry and read my e-book version.)
It's not perfect but it's a pretty nice product. I kind of wish they had WiFi in addition to the Whispernet so I could use the web features outside of cell coverage or outside the US. My clip on LED light works ok for night reading but I would like to see a slicker, slimmer, neater solution. I'd also like a cover for it that offers protection but is a little easier to slip into a coat pocket or one of my cargo pockets. So far I'd have to say, yes I'm happy with my Kindle!