really? CPU usage is pretty easy and you can see this in most OSses directly. 100% CPU usage is full :) Load isn't that much harder. It's just the load of the scheduler queue. So if some needs a rule of thumb

safe CPU load = number of cores/processes * 0.7

theoretical optimal CPU load = number of core/processes

Everything above should really be investigated because you entered the zone where  additional CPU load can drive your machine unresponsive. 

You have less CPU usage but high load? Investigate I/O usage! 

I know you know that, Sven. I just wanted to mention it because this comes up from time to time. Compared to memory consumption, CPU, scheduler and I/O are easier targets IMHO.

For Phil the point isn't the health of the system. It is EC2. You have to pay for the CPU usage on EC2 so I think he had the impression there is room for improvement. And indeed there is. But if you calculate it through it isn't really a factor.

Norbert