Get the Paperwhite. It's wonderful to read on, in any light. I've had a Kindle Keyboard, Kindle DX, iPad, Nexus 7, and Kindle Fire (original and HD), and the Paperwhite is far and away the best device. It also fixes a ton of the refresh-related issues with the recent Touch generation.
The only downside is PDF viewing, which you should still leave to device with more serious CPU and some auto-crop and fancy scrolling support (e.g., by quarter-pages).
So I've only ever had the keyboard version and was wondering about the page turn buttons. Are they gone in paper-white? Do I have to reach across with a second hand and swipe to turn the page? Because if that's the case I won't be getting one.
Part of the good thing about the kindle is that I can just hold it still and keep reading, especially useful in bed.
They render fine, but the page speed update is just a bit too slow, particularly if you read PDFs that have frequent references to figures that are 2-3 pages distant from the referencing text.
The only downside is PDF viewing, which you should still leave to device with more serious CPU and some auto-crop and fancy scrolling support (e.g., by quarter-pages).