I love my Kindle, my boss has the Nook and I'm not as impressed with that one. With regard to Wi-Fi, get the one with 3G because if you're sitting in your doctor's office you aren't going to be able to download books unless he has Wi-Fi in the office and then you'd probably have to as for a password in order to be able to access his Wi-Fi anyway.
3G is just like a phone, you get a signal anywhere. I would wait just a bit to see the new Kindles coming out. There's supposedly a touch screen Kindle and also the Kindle Fire which is kind of like an I-Pad which I have no interest in. I have one of the older Kindles and would like to get the new E-Ink technology which is supposedly better contrast. Also if you really don't like advertisements don't fall for the Kindle that sells for a few bucks cheaper because it includes advertisements that will show up on your Kindle. To me that would be extremely annoying.