I have had Republic Wireless for the last 3 1/2 years. True you used to have to buy their phone. That is no longer the case. I would be lying if i said I never had quality issues but that seems to be a thing of the past. If you happen to be somewhere where you can't get coverage usually you can find a place with free WiFi and it will work great. With their Anywhere* app i can also get and give calls and texts from my tablet and laptop if they are connected to WiFi.
* Voice may only be for the bet version of Anywhere.
They are worth looking into.