All the books you purchase for your Kindle are stored in your account online so if something happens to your Kindle, you still have all your books. The screen on my first Kindle got a glitch in it after having it for 6 months and Amazon replaced it in 2 days for me. I just had to register the new one and then sent all my books to the new device. Very easy. Also, this allows you to purchase more than the 1,500 it holds, you can swap books from your online account to your Kindle when you want to read it.
As for using the iPad as an e-reader, I have heard bad things. A friend of mine has both a Kindle and an iPad and he tried to read at night off the iPad since it is back lit. It really hurt his eyes, so he no longer uses the iPad as a reader... he sticks to his Kindle.
I do have a complaint about my Kindle... but it is more to do with Amazon and Penguin Publishers... they are in a dispute and all their books have been pulled from the Kindle
After waiting a year for the next Black Dagger Brotherhood book, I can't get it! Same with the next Sookie Stackhouse book!!! I'm very annoyed and frustrated over this!