I LOVE my Kindle :) I got it for Mother's Day this year and it was a great purchase! I pay anywhere from $0.00 - $10.00 per book, with most of them being under $5.00. About 15% of the books on mine right now were free and just like any other book, some were worth reading and some not.
I did miss the whole page turning thing for the first week. Plus, it is thin, so it doesn't have the "fatness" of a book. Finally, when you read a book, the farther you get, the less pages you are holding in your right hand - with the Kindle there is no change (obviously). The first book was the toughest and by book three, I didn't even notice anymore. Now, 35 books later, I can't imagine reading any other way!
The books stay in your on-line account with Amazon so if you delete a book, you can reload it later to re-read. However, each publisher sets an amount of times you can reload a book so find out what they number is before deleting anything off your Kindle. I haven't deleted anything yet, but I suppose at some point I will.
The best thing? I can have 5 books going at any given time all in one compact spot - the page that I left off at is saved in each book and I can backtrack if it has been awhile since I started reading. Also, I usually take about 25 books when I go on vacation . . . wow, I cut my suitcase weight in 1/2 on my last trip!
My mom has the Nook (Barnes and Noble) and she likes hers, so I think that would just be a matter of choice if you are debating between the Nook and the Kindle.
Good luck and happy reading!