Exactly, looking at the load curves over time is useful to gauging how well you are doing overall and for spotting potential trouble issues but when it comes to

Exactly, looking at the load curves over time is useful to gauging how well you are doing overall and for spotting potential trouble issues but when it comes to actually dealing with these issues or predicting an eminent collapse i tend to look at mysql threads and performance, the slow query log, concurrent users, etc. for determining what needs to be dealt with and what will hit us on the head in the near future.