All in all, the purchase was a success and may even save me money. Since I moved and did not get cable TV at my new place, I have been buying about one paperback a week: that's about seven or eight dollars a week. Since I bought the PRS-505, I've read nothing but free books. So far I've finished a collection of books and stories by Keith Laumer called "A Plague of Demons" that I downloaded from Baen Free Library (thanks to Foxfier for the reminder) and I've finally read "Dracula" which I downloaded from The Guttenberg Project.
Reading is very nearly as comfortable as a paperback but not quite. The disadvantages I've seen so far are
(1) contrast is not as high as black print on white paper,For me, the disadvantages are outweighed by the advantages:
(2) glare is a bit more noticeable than it is on non-glossy paper,
(3) the device is heavier than a paperback (but I have read heavier hard-covers)
(4) there is a slightly distracting delay and flash when you turn the page
(5) you can't always find the books you want as e-books
(1) it is more compact than a large paperbackFor other people, the fact that you can buy new books and download them from the internet would be an advantage, but it is not an advantage to me. I like going to book stores.
(2) whenever I have the device with me I have several thousands of pages of reading to choose from
(3) I now have a convenient way to read all of the free ebooks that have been too awkward to read before.
My overall reaction is that the technology still needs some improvement, but it is adequate now. If you like older (that is, free :0) books or if you just have a long commute by bus or train and like to read, this could be a worthwhile investment. Of course if you are just a technophile, you don't need those kinds of justifications, just the assurance that the technology actually does what it claims. As far as I am concerned, it does.
UPDATE: I'm having second thoughts now that I have actually tried to buy something for the PRS505. The limited selection of formats is turning out to be a problem.