Even though Server.app on 10.8 Server seems more simplified than prior versions of OS X server, there are features which have been expanded upon and made better. Alerts is one such feature. In the past, what you could get alerts on was somewhat limited, but in 10.8 Server this has been expanded.
Charles Edge goes over the fine details regarding alerts in 10.8 server, including general setup as well as diving into notification options and fine tuning what will trigger a notification. Overall, it seems like Alerts got some well-needed feature updates. This should allow busy admins to stay on top of expiring certs, full disks, network configuration changes and many other items.Source: krypted.com