I do the Force Strong Passwords plugin (http://wordpress.org/plugins/force-strong-passwords/). I just read about WP 3.7 switching to zxcvbn. My plugin replicates the current password strength JS in PHP, in order to do server-side validation on the user edit screen, and force strong passwords to be used for users with "executive" capabilities.
A quick look at the zxcvbn script tells me replicating this might be a tall order! I can't see any attempts to port it to PHP around. Are you aware of anything like this? Any plans to implement something to force strong passwords in your zxcvbn plugin?