I saw this mentioned on another blog (I don't remember which one) over a year ago and thought it looked good, but didn't provide much info beyond what I was getting with VKernel and RVTools. Now I'm wrong. Alan over at http://www.virtu-al.net wrote a PowerShell script that checks the health of your vCenter environment. It has recently been updated to handle plugins. Most of the checks have been converted to plugins, and now there's an Exchange plugin written by Phil Randal. I would not be surprised to see other plugins for other systems like AD and SharePoint in the future.
I'm running most of the VMware and Exchange checks. This is providing me information beyond the VKernel and RVTools tools I currently use. I've set it up to run once per week and email the report to our VMware administrators distribution list.
In just the first week is has brought several problems to light which will be subjects of future blog articles(!).
I highly recommend!