Using DFM/Ops Mgr as the primary method for monitoring and problem notification. I do have a modified SNMP script for collection in Big Brother (not officially supported by NetApp). We will soon be moving to Nagios, which is supposed to have better interpretation of NetApp mibs. For example we had to turn off Big Bro's monitoring of environmental data points as it continued to report temperature issues where there were none.
Another way you can monitor NetApp is using SCOM / OpsMgr management pack, or solarwind NetApp Profiler. I have used the older version of Profiler in the past and it worked very well. Those are some of the things you can consider and of course budget is important factor. SCOM requires a lot of planning and it makes Changes to AD. I think SolarWind its better option if you already own the product.