Boost Mobile Coverage & Network

Much like Virgin Mobile, Boost Mobile is owned by Sprint and utilizes their network. In addition to 3G speeds, this carrier does offer 4G LTE connectivity to select markets, with more expansions happening monthly. It's worth noting that the Sprint network is not nearly as complete as some other companies like Verizon or AT&T, so be sure to check the coverage before you sign up.
As far as locations that have a lot of coverage, well, there aren't many. Indiana, Illinois and Ohio have the best coverage followed by some of the northeastern costal states. Florida, Texas and Michigan have decent coverage while the rest of the United States has spotty coverage at best. Generally, Boost Mobile's coverage seems to follow the interstates in low coverage areas, so depending on where you live and travel it might not be a bad choice.
Because Boost uses Sprint's network, they utilize CDMA bands instead of GSM. This is important to know because the CDMA network is generally not available internationally–it is mostly only in the United States. However, as far as speed goes, there is not much difference between the two networks–so it really only matters on where you intend to use your phone.
Phones created specifically to work on the CDMA network generally don't have removable SIM cards. These phones must be unlocked and reprogrammed in order to access a different CDMA operator. Keep in mind, however, the currently Boost will not unlock phones and claim that they do not have the ability. So, phones purchased through Boost can ONLY be used on their network. The ability to unlock Boost phones is expected sometime in 2015, as required by law, but older Boost phones may still not be able to be unlocked after that time. Currently, phones can not be brought to Boost Mobile from other carriers. Only Boost Mobile phones can be activated and used with Boost Mobile's network.