I've read over a dozen books on my iPad, but I use it for far more than just iBooks. I watch a lot of movies and tv shows on it when I travel, email, websurfing, newsreading, the occasional magazine too...even a handful of games. Apps like Open Table and Yelp are absolutely fantastic when traveling in some newish city. I also use the iPad as my primary iPod device these days, despite having an iPhone, simply because I can be listening to music while I'm using the iPad for some other type of reading or browsing at the same time. You really don't often need any other device than this one for a whole host of things. I love it.
The OP asked about eyestrain though if I remember correctly. As other posters have mentioned, it doesn't seem to be an issue at all. I've sat and read for 5+ hours at a time, only to take a "break" from reading by watching a movie on Netflix...on the same iPad (heck, even on the same battery charge no less). I've not had any issues and haven't noticed my eyes bothering me at all.
My wife on the other hand uses her iPad to read a great deal more than I do. She is an avid reader and can easily go through a book a day. She uses her iPad for most of this reading (she didn't want to share mine, so she got her own). From time to time though she also uses her Sony reader still. She liked it better than a Kindle when she bought it and the Sony is the only device that currently can download books from the local public library to read for free instead of always having to buy books. (When will this software be ready for the iPad !!!!??? It's currently still in development). Lastly, she uses the Sony while down at the beach. It's small, relatively inexpensive (if it gets ruined, no big whoop), and she tosses it in a ziploc bag to limit the chance of sand and salt water splashes getting in/on it. I don't think either of us would be comfortable putting a more computer-like device like the iPad in a ziploc to use constantly in direct sunlight for hours on end.
So ya, the cheaper devices (Sony & Kindle readers) DO have their uses. But anyone trying to imply that either would be a preferred device over the iPad really doesn't have a clue. I'd guess the term "Kindle fanboy" hasn't caught on in the lexicon because the whole concept just seems kinda ridiculous when you think about it.
I think of the Kindle/Sony as being similar to a piece of chalk. Sure chalk is probably the single best writing implement for a schoolroom blackboard, but an iPad is so much more. An iPad can be a pencil, a pen (in any and all colors!), a paintbrush, a magic marker, a stenography device, and a highlighter all at once. "Oh, but chalk is better on blackboards! Take that iPad!", ahem, sure. Ok. Whatever.
If someone is going to do 100% of their book reading outdoors at the pool, grab a Kindle or a Sony reader and be happy that you made the right choice. If, however, a purchaser is like most other human beings and will likely use it elsewhere as well (like say, at night when a Kindle is utterly useless)...and is also in the habit of using a computer for some of their normal daily tasks, the iPad is simply far and away the superior choice for pretty much every conceivable way you could possibly want to use a reader or even a light computer. Hands down.
