I recently acquired a Sony PDR-505 E-book reader.
My wife just received her Kindle 2 from Amazon today.
Let's see how they compare, shall we?
As you can see, the Kindle is larger than the Sony, to accommodate the built-in keyboard. The screens are both the same size, and because they use e-ink technology, they look like an off-white, glossy book page.
Despite being the smaller of the two units, the Sony is actually heavier. This is because the Sony has a metal case, where the Kindle is plastic (making it very very light).
Controls The Kindle has a Next Page button on each side of the screen (good for leftys and rightys), with a Prev Page button above it on the left and a Home button above it on the right. This arrangement might be a bit confusing - I imagine trying to turn back and ending up on the main menu instead of the previous page.
Also on the right edge, the Kindle has a Menu button (brings up a pop-up menu, similar to a right-click in Windows) and a Back button (takes you back to the previous screen, not the previous page). As these buttons are separate from the page navigation buttons, there's no danger of hitting Back instead of Prev Page.
Next to Menu and Back, there is a tiny 5-direction joystick. This is used to navigate the Kindle's menus. "Clicking" with the joystick selects whatever you have highlighted.
At the bottom of the Kindle is its keyboard, something that other e-book readers don't have. This is useful for buying/downloading books directly to the unit, and for using the Kindle's built-in web functions (more on that later).
The Sony's controls are similarly straightforward. The page navigation buttons are arranged for left or right handed use: There are forward and backward buttons on the right edge, and the large circular button on the left side beneath the screen also has forward and backward buttons.
The menu button is located on the right side of the unit, next to a larger, circular button that is used for controlling the cursor (similar to the Kindle's joystick).
Additionally, there are ten buttons along the side of the screen, used for making quick selections from the menus (menu items line up with these ten buttons).
Control responsiveness is pretty much the same for both devices. Page turns, screen changes, etc always take a second or so - this is an inherent limitation of e-ink technology. This delay, however, is not intrusive. It's about as long as it takes you to manually turn the page in a standard book.
Readability The Kindle will produce better images - it is capable of 18 shades of gray, compared to the Sony's 8 shades.
This, of course, makes no difference at all if you're not looking at pictures.
Included accessories The Kindle comes with an AC adapter and the unit itself.
The Sony comes with a USB cable, a soft case, and a CD with Sony's Ebook Library software (imagine iTunes for books)
Web functionality The Kindle has a built-in web browser, which doesn't require a WiFi connection. It uses Amazon Whispernet through Sprint's 3G network. It's not the fastest internet, but it's free and it does work: The Sony has no web capability.
Text-to-Speech The Kindle has Text-to-Speech. In other words, it can read your books to you.
It had both male and female voices, and can read at three speeds. The voices sound human, but they don't always pause in the right places - like at the end of paragraphs.
The Sony has no Text-to-Speech.
Other functions When it comes to built-in storage space, the Kindle is the clear winner - it can hold 2 GB, compared to the Sony's approximately 200 MB. This is mitigated somewhat by the fact that the Sony is able to read Memory Stick Duo and SD cards (up to 8GB and 2GB respectively).
You can upload books to both devices via USB, but only the Kindle allows for wireless uploading.
The Kindle also has a pre-installed dictionary, which can be accessed while you're reading a book. The Sony has no comparable function.
Additional Kindle features with no Sony equivalent include the ability to make notes and add highlights to your books.
I'm not going to compare the built-in MP3 players here. Because everything has a built-in MP3 player these days (I think there's even one in my toaster), it's a moot point.
Conclusions Clearly, the Kindle is the heavyweight in this fight. It has the ability to access the web from anywhere in the US, it can download books on the fly, and it can even read those books to you. It's biggest drawback is that it doesn't come with a protective cover - you have to buy one separately ($25 and up).
The Sony may not have as many features, but it does come with a cover, and it costs less. The Kindle costs $359, and I got my Sony from Wal-Mart for $275.
Ultimately, this comes down to which features are important enough to pay for. If you want web access and Text-to-speech, than you'll probably be better off with the Kindle 2. If, however, these functions don't matter to you, then you'll be better off with the Sony.
Bear in mind, these devices are still quite new. I'm sure that I'll have more observations on them in the future. Feel free to ask questions in the comments - I'll try to answer them the next time I write about these readers.