Well, posts 3, 4 and 17 kinda nailed it (except for the Kindle part in #17--I don't want wireless and I enjoy the longer battery life of the Sony).
For me, I've always been an avid reader--scifi (syfy?), mysteries, spy novels, science books, humor, travel, some history & biography. I have a big set of overstuffed bookshelves to show for it (6 6.5' high shelves, mostly 2-deep and crammed, plus many boxes!). But in recent years, between work, going back to school midlife, web addiction, DVDs, etc., I was doing much less leisure reading. This changed around 2 years ago when I got my first Reader. It has been great for me. (I still read some p-books, btw.)
Pluses (Sony Reader, now a 505):
* Great display, easy on the eyes (I couldn't read an lcd all day for fun!)
* lots of reading choicesat my fingertips
* Great (3-week+) battery life; no need to constantly charge like a phone or laptop--just take it along and read!
* Instant on to pick up where I left off, great for short reading intermissions (like on the subway)
* Multiple bookmarks for when I'm in the middle of more than 1 book
* Adjustable font size
* Smaller than a single regular book (thin!) but holds hundreds
* Great for travelling--short and long trips. Just take it along.
* Discovered lots of authors from online book sources (mostly free/borrowed, some I bought)
* Instant access to the NY Public Library e-collection. Great!
*Easy 1-handed operation.
*Works in my steamroom! (Inside a ziplock bag) Try THAT with a p-book!
* Gets me to read more, even with all my other books on the shelves.
All in all, it has been and continues to be a great value for me. I'll add that my gf has access to many books in Russian through her Reader too.
Funny how the "long-time lurkers" pop out of the woodwork to rant!
But seriously, it looks like there will be more e-book device options that will become cheaper in the coming years. And, hopefully, some sort of standard format (ePub) to give users flexibility in their device choices. Amazon made an interesting choice with the big-screen Kindle DX, and I think SOny is getting it right now with the upcoming 300 and 600 models--a compact less-expensive reading device, and a fuller-featured one with touchscreen and dictionary/annotation capability.