Amazon overreacted to the kerfuffle that it was "too easy" to turn pages on the Kindle 1. Bezos didn't just change the size and position of the buttons. He changed their nature completely.
The buttons aren't any longer "panels" along the outside to which you apply gentle pressure, like tightening your grip on the device slightly. (That's how I'd describe the Kindle 1 buttons).
The Kindle 2 primary buttons are "rocker switches" facing *inward*. So, to turn the page, you must apply (not at all gentle) pressure on a very precise position, in the 25% of the button's area along the inside of the device. The less precisely you position your finger, the harder you have to press.
About the only finger capable of doing this conveniently is the thumb of either hand. You can press with the fingertip proper, if you bend your thumb to an extreme angle, or use the fingernail. Or you can apply pressure without bending the thumb, if you assume a precise position, with the thumb at the first knuckle above that spot.
Any of these movements can be very hard and painful to do if you have any repetitive stress pain, "carpel thumble", or regularly feel sore after a long blackberry session. For some users, it will be agonizing. I think the buttons will bother any user, over time -- they're just so darned inconvenient. A world of difference that will stun many who used the last version.
Turning pages is a chore instead of a pleasure, and takes three times as long as with Kindle 1 unless you hold a fixed position with your hands -- as you have to struggle to get your thumbs into the right place every time. I've found it so much harder to turn pages that it defeats the faster rendering.
I can't comfortably read for longer than about an hour, if I've done too much typing or texting the same day. After late night reading last night, I woke up with significant finger pain.
Adding insult to injury, with the news that Amazon is withdrawing universal availability of text-to-voice, users who suffer finger joint pain with Kindle 2 just can't catch a break.