This may come as a surprise to some, since Sprint does allow customers to do "ESN (Electronic Serial Number) Swaps" from one 3G device to another without changing your contract. Many people assume that they will be able to do an ESN swap from their 3G device to a 3G/4G device, continue using their unlimited 3G service for the time being, and be ready for 4G when it becomes available. This is NOT the case. You cannot do a simple ESN swap from a 3G device to a 3G/4G device. You can do a swap and not extend your contract, but you must change the plan to the 3G/4G plan (also, the swap can't be done online; to swap from a 3G to a 3G/4G device, you have to call Sprint).
For people that live in a 4G area, this isn't a problem since the 3G/4G plan provides unlimited 4G access, but for people that will mainly be relying on the 3G side, giving up your unlimited 3G service might not be worth making the switch just yet. If you have a 3G device with an unlimited Sprint plan and are considering doing a swap to a 3G/4G device, you should only do so if you actually have access to 4G and plan to use it; otherwise, you may want to wait until 4G is available in your area. You can keep up to date with the latest news on 4G, including coverage rollouts, by visiting our sister site 4ginfo.com.
For those that are ready to upgrade, you can purchase the U301 and the Sprint Overdrive both with and without contract from 3Gstore. Click here to purchase with no contract; if you're looking to purchase with a new two-year contract please use the 3gstore Sprint Order Form.
For more info on Sprint's 3G vs 3G/4G service and devices, check out our video debate: 3Gstore Mobile Break.