vSphere 5 compare with vSphere 4
HA Admission Control Policy
The Admission Control Policy for vSphere 4 as shown on the left in the percentage of cluster resources is fixed and irregardless of CPU or Memory the percentage is applied for both.
In vSphere 5, notice that the percentage has be split out to memory and CPU. This updated percentage options, helps eliminate when you have like to specific different amount for CPU and memory with different tolerance.
Virtual Machines Options
In the Virtual Machine Options, in was leave VM shutdown as the default value whenever Host Isolation is detected. Many of my customers actually thought this was the default value recommended by VMware and leave it as it is however whenever a host isolation is really found, their VMs was shutdown.
In vSphere 5, the defaul value is now changed to Leave powered on. I believe, VMware has found that many cases found that VM was shutdown whenever a host isolation happens and decide to put it as default instead of Shutdown and affect production VMs when they are still accessible by any chance.
One of the feature that remain unchange was VM monitoring. In vSphere 4, it was default as disabled. However monitoring was a recommended though. However, majority of the customers are worried of sudden restart of their VMs and never ever used this feature.
Same thing in vSphere 5, this was left unchanged. Monitoring is via the heartbeat sent from VMware Tools and most customers like to keep it as it is unmonitored and use a third party monitoring tools to perform this job more efficiently. I believe VMware would most probably thinks that this is still eave as disabled unless customers themselves knows what they really want to do with this feature.