We found the calendar Week and Month statistics difficult to interpret. So we changed that to Last 10 days and Last 30 days. And added Last 100 days. Note that for all of these you can compare each period by dividing visitors by days. Thus having a single number to compare (visitors per day). (In the example below it shows a fairly consistent 1.5 visitors per day for all periods.)
We also extended the graph out to 15 days to give more days and to allow you to adjust for weekly patterns.
Hope you find these changes useful and an improvement.
(These changes are possible due to the open and sharing nature of WordPress add-ons. WP Power Stats add-on was adjusted.)