All "Nexus" branded phones ship locked but are trivial to unlock. You just plug into your computer and run a few commands.

There are two different Galaxy Nexus phones: the CDMA/LTE version (offered on Verizon and Sprint) and the GSM/HSPA+ version (offered without contract on Google's home page for $349).

The GSM/HSPA+ model is directly supported by Google. Google releases new versions of Android and pushes the changes directly to you. Or you can grab the appropriate files, copy them to your phone, and install them. The AOSP (Android open source project) code builds an image for the GSM/HSPA+ Galaxy Nexus, out of the box.

The CDMA/LTE model was supposed to be supported the same way, but then Google and Verizon had some sort of pissing match. Consequently, if you want to be bleeding-edge, you need to install crap manually, like I did. For better or for worse, these two Galaxy Nexus variants are sufficiently similar to one another that the hacker community was able to take a memory dump of the GSM/HSPA+ variant and mod it to run perfectly on the CDMA/LTE variant. That's what I'm running today.

Now that the public repository has been updated (yesterday) with Android 4.1, the big distros like CyanogenMod will start working it into their own build plans.

If you were a basic Verizon customer with zero interest in any of the sorcery required to update your phone yourself, Verizon would eventually get around to shipping you a new build. Ultimately, this is the only path that people like me have to getting updates to the closed-source parts of our phones (radio drivers, etc.).