You get one because it provides an extremely value function. Using a laptop with 3G while mobile on the road, no thanks. I tried that method and a tablet is superior.
While static a laptop is a better choice for doing real work.
While static and simply browsing the web, or reading, or checking travel reservations, etc., a table is superior.
The Kindle seems to have good reading capability, but when you can buy a more functional tablet, why throw your money away at something with limited options?
Stick with a Kindle if your happy with e-reading and active web browsing. If you want to do a lot more go with a more fully loaded tablet. iPad leads the pack at the moment. Most certainly, the a Kindle will add more features; Android-based would be a good move.