Republic Wireless: Currently only offers 1 phone. Motorola Defy XT which is a good phone except for 2 drawbacks: 1) Limited memory - can't install many apps, especially if you allow the Google Play Store to update the factory installed apps. This can be overcome by rooting the phone and using Link2SD, but that is NOT recommended unless you really know what you are doing. And 2) Overheats easily (causing lockups and reboots). Running multiple heat-generating things like WiFi, Bluetooth, cell, GPS, and charging at the same time can trigger the built-in overheat protection.
There are also a lot of limitations with the service itself. Cannot start (or worse, stop) messaging with short message codes (text to 5 digit number), no MMS support, and doesn't transitions calls between Cell and WiFi modes (using VoIP when in WiFi range - drops call when you walk away from WiFi - does automatically re-call all parties though to get things reconnected).
What you choose to pay for the phone determines the monthly service plan price. Choose to pay $199 for the phone, the service will be $19/mo + taxes. Pay $79 for the phone, the service will be $29/mo + taxes.
Talk, text, and data are all truly unlimited. They will drop anyone though who is caught tethering.
Coverage is Sprint's post-paid network, including all roaming areas (meaning, you get coverage by Verizon and local CDMA carriers wherever Sprint doesn't have a signal).
If you can deal with a limited phone, and quirky service, it isn't a bad deal. If you don't like to troubleshoot phone issues on a daily basis, then look elsewhere.