To change pages with your left thumb you don't have to move it all the way to the right - you can make a little swipe motion on the left side of the screen and it will skip a page.
I used to have the Kindle Keyboard(Kindle 3) and my god, its resolution was driving me crazy, like it was never sharp. Paperwhite is a lot better in that regard. HOWEVER - fonts get really jaggy after a few page turns, and that's because the paperwhite only refreshes the entire page every 5 or so turns. You can go to settings and tell it to refresh the entire page every turn - then the fonts are always super sharp.
From my personal perspective - I would NEVER trade my paperwhite back for the Kindle 3. I don't mind the lack of physical buttons, and the backlight makes it fantastic.