I didn't buy a Kindle, but can tell you, if I was hauling to the beach for reading--would rather sand got in my Kindle than in my iPad!
Think one of the best marketing strategies Amazon had with Kindle is having an app for computers, phones, iOS, etc.
What I personally don't like about Kindle is there is little consideration of privacy. My colleague's experience was when her husband logged on to her Kindle--she now had access to his archive. If you don't want people to know what you're reading, the only real way to deal with it is to have Kindle periodically kill your account. Kindle does not let you permanently delete content from your account--it lives in your Archive or your online Media archive. I actually talked to a tech at Amazon--if you can believe it--by phone last year. Told me the only way to delete my books was to delete the account. Apparently Amazon doesn't want to have to reload books people delete then want to have back. :-s