Sheeri Cabral, an active MySQL blogger and two-time winner of MySQL Community Contributor awards has written a great review on MONyog.
Our favorite highlights:
As an overall review — MONyog is the best out-of-the-box GUI monitoring tool for MySQL that I have seen. It “just works.” As promised, getting up and running quickly is easy, and having a centralized location for monitoring is very useful. The graphs are beautiful and the statistics that are graphed are useful time-savers.
The biggest difference between MySQL’s Enterprise Monitor and MONyog is that MONyog is agentless. At Pythian, we have many clients with differing security requirements. Requiring a daemon process to be running is not something we currently do, and it might be a hard sell for some clients. Even if every client was amenable to it, making sure the daemon is up and running on each MySQL server is tedious. Note that agentless operation works for every feature, including log analysis as well as operating system statistics.