Worth it? YES, every bit of it. So far it is all I envisioned and more. Does it mean no more book buying? NO, absolutely NOT, but it is a handy gadget to have when a lot of the books you use are public domain, several in Kindle format, many in PDF.
Are PDF books very comfortable to read or navigate? Not as much as Kindle books, but if you put it horizontally they are certainly much more comfortable than to read from the computer screen or laptop.
I have increased my reading, I LOVE my Bible reading with a comfortable font and light weight. I use and old light that consumes the batteries in a night and a half, but NO PROBLEM, I have two sets of rechargeable batteries and I never run out of light.
Fun moments: Our evenings cuddled in bed with the girls taking turns to pass the pages of the Kindle and holding a flashlight, and reading The Seven Little Sisters Who Live in a Ball...
Interesting things: I have read again or finished reading several of the SCM free booklets and Stephanie´s free biography of Charlotte Mason, (look under free stuff) and it was very pleasant to do.
Curiosity: I can read your blog posts, and I do occasionally, from it.
Bonus: There are not many Kindle books in Spanish, but there are several precious PDF books, poems, fables, etc, that are great to read for free.