I have one. I LOVE it. I have a walk in closet FULL of shelves of paperbacks and I just ran out of room. I thought I would miss my books but I don't really notice I'm reading a Kindle. I'm a migraine sufferer, so I'm sensitive to monitors and multiple light sources. I've never gotten a headache reading my Kindle. It's just as easy on my eyes as print. It's nothing like a computer screen. There's no backlight at all. I use a book light at night just like I used with my regular books.
Wifi works fine. That's what I have. Don't expect to surf the internet on it too much (it's very basic and can be SLOW) but getting books takes seconds. Navigating the Kindle store is easy.
My only advice and bad experience with it is this: Never leave it on the floor. Ever. I left it on the floor under laundry, stepped on it, and cracked the screen. I had to get a new one.