Switching orientation to landscape makes most of my PDFs readable, at the cost of scrolling three times per page. It's not fun, but if necessary you can put up with it.
I use Readability to take web pages, get rid of pagination and beam the raw text to my Kindle, and I love it.
It works fine when you have a clean PDF with nothing but serial text (e.g. a novel).
Completely useless if your document is a less than perfect OCR job, if it has reasonably complex tables, math or non-Roman text (especially laid out in parallel with English translation). In other words, there's basically no way to read physics or Chinese philosophy papers from JSTOR with it.
Your average programming book might make it through okay, but might not. At the very least it's going to kill the indentation of any code samples (very bad for Python books).