Disclaimer: I own a KindleDX and am incredibly happy with it.
you have a lot of good points, but there are some things that you fail to recognize:
For one, the size and weight of books. For a casual reader, the KindleDX is overkill. It's large, expensive and the benefits don't outweigh the hassles (recharging, fragility, etc). For those of us that have large libraries of tech books, the KindleDX allows us to store our entire bookshelf on a single device that takes up less room and weighs significantly less than a single book.
This brings me to my second point: The Kindles (an ebook readers in general) have better displays for reading large quantities of text. It's easier on the eyes than a laptop. Also, for those of us that use mass transit to commute and don't always have a seat, a laptop is not an option. Have you ever tried to stand up in a crowded subway and use a laptop? Even sitting down and using the laptop is a pain. Laptop battery life is also significantly worse than the Kindle's--my kindle hasn't needed to be charged a single time since I got it nearly 3 weeks ago. It also beats out the laptop because you can travel light with it; you don't need to carry a laptop bag. All you need is the device, and since it doesn't require frequent charging, you don't even need to bring the charger (USB cable) with it.
Third point: When using ebooks for reference (or following a tutorial in the book) while you're doing work on the laptop, it's nice to have a separate device. This was one reason why I stuck to buying physical books rather than purchasing PDFs exclusively.
So, while $700 (KindleDX + tax + shipping + 2 year warranty + sleeve) is quite a steep price to pay, for those of us that will use it a lot, it's worth the price. If I wasn't in such need for the solution, I would have held off a year or so and waited for it to come down in price or for a cheaper solution to be released.
My coworker picked up the Sony PRS-700 a couple months ago and he's mostly very satisfied. It was around $375 + tax, but has a significantly smaller screen. Although it's got a touchscreen, the touchiness is kinda flakey and it's got some weird glare because of the touch surface. Also, PDF support in the thing is mediocre--the zoom sucks and it really needs a larger screen.
I was going to hold out for the PlasticLogic (http://www.plasticlogic.com/) but I was hoping for something that I could get real books on, too. Since I really liked the Kindle (my dad picked one up last year) and the features that come with it (cellular websurfing/wikipedia/wireless book delivery and books that you can buy FROM the device), I opted for the DX.
Like I said, the DX isn't for everyone. It's pretty big and it's expensive, but I feel that I'm definitely getting my money's worth.