Best way to monitor a VMware virtual infrastructure (Community supported)

Hi guys,

What is the best way to monitor a VMware cluster with a few hosts and a vCenter appliance (where monitoring of the vCenter also is critical since it's used for snapshot backups by a third party application)

I've looked at http://wiki.zenoss.org/ZenPack:VMware_ESXi_Monitor but it seems to skip the vCenter and connect directly to the ESXi hosts. And the vSphere ZenPack is only available in the commercial version of Zenoss with it's in my opinion ridiculous licence model.

Cheers,
/Stefan