It might have taken just short of "forever", but Verizon has finally opened up its arms to unlocked iPhone and Nexus 6 owners who want to activate their device on the carrier's network. It seems the fact that the company was effectively pushing customers away got to be too much, so it's reversed course.
Flickr: Robert Scoble
In order for someone to bring their iPhone or Nexus 6 in to Verizon and activate it successfully, it has to be unlocked. If you've never gone through the process of unlocking your device before and are not sure whether it actually is locked, you can use Verizon's activation tool to find out for sure.
If you discover that your phone isn't unlocked, you'll have to get ready to cough up a fee to make it so. Usually, the carrier that you bought your device from will offer this service, and some admittedly charge a ridiculous amount - I've seen it as high as $80. If you're brave, you can scout out a third-party service online, but those are considered unofficial sources (even so, I've used such services for multiple devices without issue.)
It's worth pointing out the fact that when Verizon bid for the 700MHz spectrum, it assured us all that it'd allow customers to bring any device to its service that met its 'minimum technical standards'. That's great - but eight years later? That's not so great.