I don't know if this point was ever really clarified in here so I thought I would.
Regarding the 4.5 for Powerseller status, it is NOT the average of all four scores. You must have a minimum of 4.5 in each of the four scores. So you could have 4.9 in three of them and 4.4 in one and you're out. I don't know though if they give you a certain time period to shape up before they boot you similar to the sales quota does now.
This came up during one of the audio sessions when the changes were first made. It is not the average, it is 4.5 in each one. Same thing for applying the discounts, it is not based on the average of all four. The figure they quote, 4.6 or 4.8, is required as a minimum in all four categories.
When you find doing what's right hard to do - you've got a problem.