If you are looking for an Enterprise Monitoring Solution for your VMware environment , make sure you watch this video about Best Practices for Monitoring VMware with System Center Operations Manager.
And request an evaluation key here to find out for yourself. This is by far the most scalable and advanced monitoring solution for VMware you can find.
Extra information can be found here…
And a lot of recourses (like datasheets, whitepapers, sizing calculator etc) can be found here…