How do you know what vSphere Family product is compatible with another?
Does ESX 3.5 work with vCenter 4.0? Does Capacity IQ 1.0.2 work with ESX 4.1?
Here you can see the vCenter 2.5 U6 compatible only with ESX 3.5 U5.
And here you can see the Capacity IQ 1.0.4 is the only version compatible with ESX 4.1
I find it a useful tool!