I was able to get the agent working, but it was not straight forward and I had to work around an issue with how the agent is packaged.

I haven't tested it on a RHEL7 box yet, but on CentOS 7 and Oracle Linux 7, the agent package from repo.zabbix.com does not work out of the box. The only changes I made to the configuration files were Server, ServerActive, and Hostname. This works for all RHEL5 family, RHEL6 family, FreeBSD, HP-UX, Debian Squeeze, Debian Wheezy, and Windows Serve 2003/2008/2012 systems that are not using custom items.

To fix the problem, I had to comment out the UserParameter lines in /etc/zabbix/zabbix_agentd.d/userparameter_mysql.conf that the package installs.

The only symptons I saw other than the agent not going green on the host configuration web page were these lines in the server log file:

 21168:20150522:065538.362 cannot send list of active checks to [X]: host [X] not found
 21150:20150522:065843.644 Zabbix agent item "agent.ping" on host "X" failed: first network error, wait for 15 seconds
 21163:20150522:065858.750 Zabbix agent item "system.cpu.load[,avg15]" on host "X" failed: another network error, wait for 15 seconds
 21161:20150522:065913.724 Zabbix agent item "proc.num[ntpd,,all,]" on host "X" failed: another network error, wait for 15 seconds
 21160:20150522:065928.736 temporarily disabling Zabbix agent checks on host "X": host unavailable