Good LTE band support is something you might take for granted if you are used to using flagship Android or iOS devices.
At the moment I'm wishing I'd bought the dev kit, I'd be happy with it slapped into a 3D printed case as my phone.
I know that, for instance, Verizon has certified a variety of modules to work on it's network, and a phone (or laptop) that uses that module need not be certified by Verizon to work on their network, for instance. Every Verizon compatible laptop doesn't get certified, it just tends to use one of a handful of Sierra Wireless LTE modems which are. Similarly, my understanding (and hope) is that Purism is going to support dropping in various LTE modems so that people can get support for the networks they need.