Well, as you might have guessed, it depends.
It depends on what you want to see or detect in these reports.
If you use resourcepools in the correct way, and not just for organising your VMs in handy groups, then these reports will give you quite some information on how your resourcepools are coping with the load in the environment.
Once you find a resourcepool that is having problems, lack of resources for example, then you would have to drill down to the ESXi or VM level to see where the actual problem might be.
Performance reporting is not too difficult, interpreting the reports and taking action is.
Jeez, I hope that didn't sound too much like a sermon 