Well the 3G is great because newspapers automagically gets sent to you every morning, magazines get sent to you each month (or whenever), and blog updates are sent to you throughout the day. You can't guarantee that with WiFi. All this happens whether you're sitting in a train, or on a 10 day vacation somewhere in the US. Doesn't matter if you just travelled from NY to Florida, because you'll still get all your reading material, and without the bulk.
Ok, I guess you've actually paid for the internet hardware inside, and the connection itself, but if you keep the device for 4-5 years, the additional cost over a $200 Sony e-Reader isn't much if you're going to subscribe, download books, and browse web news-sites. Of course, you also have access to Wikipedia, a free dictionary, and basic internet access to Google News, blogs, etc. It's
basic internet, but it's internet, and there's no monthly fee.
My step-dad reads a book every 2 or 3 days. If he had a Kindle, he could go on vacation without bringing 3 novels with him, and a bunch of magazines. He'd probably never need to charge his battery during his trip either, since a charged Kindle can handle 8000-10,000 page flips before running out of battery power.
iPods are pretty useless for people who don't have the desire to listen to music all the time, or don't want to watch videos on a small device.

At least with the Kindle, I could also browse Google News.
Too bad I can't get this outside the US.
