I’ve had my Kindle for about a year and I really enjoy it. I haven’t seen the others, so I really can’t comment on them.
It’s NOT like reading on a laptop or monitor - as you do need light to read. It that respect, it’s more like a book, and you won’t have the eye strain that staring at a computer screen can give you. Besides, it’s hard to read that computer screen in bed.
It is very lightweight and now has folders that allow you to organize your library, if you so desire. I like the 3G coverage at no extra charge - I can get another book any time I want.
I typically read every night and the battery lasts for weeks.
I like that I can easily adjust the font size to whatever my eyes feel like reading.
Whenever I run across a word I’m not familiar with, I can simply move the cursor to that word and I get the definition. I find I use this more than I thought - maybe my vocabulary isn’t all that great.
I really do prefer it to reading a paper book. It’s lighter and easier to turn the pages.