> Have a look at this thread, Troy Clavell has a very big site with around 133 VMs per host.
It doesn't matter how many someone else has running, they could be very small VM's. Quad Core processors allow more consolidation than Dual Core (in our experience). They key is the processors. Not VM's. 4 vCPU per Core is a recommended guide line and not absolute. As Jase said, it depends on workload, but Memory is irrelevant, because the more Windows (similar kernels) the more shared memory you have in the end. CPU is the first and foremost factor on any VM Server / Host. Memory can be adjusted tweaked on VM's, and we pretty much ignore it, also considering the swap that takes place for VM's they get their own memory anyway, but even if the host swaps, typical config is from the SAN, swap occurs on local ESX host (very fast disk speeds, you won't notice thrashing).
It all boils down to micromanagement and documentation. You should know your environment. Every VM is different, every host is different, every cluster is different, every configuration is different, and we can argue this point until we are blue in the face, one config may not work well with ALL environments, that's why you TEST first to see how the VM's react, add more, lather rinse repeat. That's really the only way to find out how many VM's you can put on the host. Then when all is said and done, and a host fails, and you are close to your limit, you are in trouble, that's why you want to leave some padding room.. no more than 70% consolidation, because in the event something happens, you won't be able to shift your VM's elsewhere.... So it's more than just nuimbers, its about planning, good implementation, and testing. The hardware is only as good as you anticipate it SHOULD be.
Respect, you don't say much but what you say is useful.