The new version of irqbalance seem to have incorrect configuration that prevents the service from starting. 

After upgrading to irqbalance-1.0.4-1.mga3.x86_64.rpm I see thew following:

[root@umka ~]# systemctl start irqbalance.service
Job failed. See system journal and 'systemctl status' for details.

[root@umka ~]# tail /var/log/messages
Sep 16 18:49:01 umka systemd[1]: Failed to load environment files: No such file or directory
Sep 16 18:49:01 umka systemd[1]: irqbalance.service failed to run 'start' task: No such file or directory
Sep 16 18:49:01 umka systemd[1]: Unit irqbalance.service entered failed state.

The problem seems to be in the file /lib/systemd/system/irqbalance.service:

[root@umka ~]# more /lib/systemd/system/irqbalance.service
[Unit]
Description=irqbalance daemon
After=syslog.target

[Service]
EnvironmentFile=/path/to/irqbalance.env
ExecStart=/usr/sbin/irqbalance --foreground $IRQBALANCE_ARGS

[Install]
WantedBy=multi-user.target

Obviously, the setting for EnvironmentFile is OK for an example, but should probably be something more specific than /path/to/irqbalance.env, most probably something like /etc/sysconfig/irqbalance