I was on a business trip in Korea for 9 weeks earlier this year. The hotel had only wired internet, but I was able to get a 3g signal for my Kindle Keyboard 3g. The plant I where I was working also had a 3g signal for my Blackberry, but wasn't a place I wanted to take my Kindle if I wanted to keep it. So, I downloaded and installed the Kindle for Blackberry onto my phone. After that, I could read at the hotel and at the plant on separate devices without missing anything. It worked well enough to read the first three books of the Song of Ice and Fire series. Although, reading for extended periods of time on the tiny Blackberry screen is not a lot of fun.
The ability to sync across devices really made me glad I paid the extra for 3g.