As a long time Sony user (I had the 500, and upgraded to the 505), I am really happy the kindle is now small enough to fit in my jacket pocket (that was the main thing I was waiting for). So far I am very happy with my Kindle 3, although I would love if the screensaver were the current book cover too. It just makes sense.
To clear the screen, slide the on/off switch and hold it for something like 7 seconds. The screen will blank. (If you hold it for 15, the kindle will reboot)
Build quality is excellent, but a cover is a good idea
. I love the buttons on both edges, and the keyboard is much improved over previous kindles. The cover attachment mechanism is genius. The screen blows away my 505, which until now had the best screen on an e-reader (the touch Sony screens were horrible), and the page turn speed is FAST.
Don't really like the UI, but I'll get used to it. I haven't tried a PDF yet.