Scott,
You are not required to use Operations Manger with the ONTAP simulator. However, if you want to you definitely can. I do this myself for customer demonstrations and experimentation. No special plugins are required to use Operations Manager with the simulator. The only time you might need to install a plugin is if you're running a version of ONTAP higher than 7.3.3. Ops Mgr comes with plugins for ONTAP version 6.5 through 7.3.3.
If you plan on running more than one simulator, make sure you change each simulator's System ID and serial number to make them unique. Otherwise, Ops Mgr won't recognize more than just one of them.
http://communities.netapp.com/message/27073#27073
Let me know if you have other questions about running Operations Manager with the ONTAP simulators and I'll be happy to help.