bluntforce - 8:35 am on Apr 3, 2012 (gmt 0)
Hourly changes do not matter if you are building for the long term, monthly changes might have significance but shorter term changes are fleeting.
Trying to determine where you should emphasize your efforts based on hourly SERP changes most likely won't result in productive site changes. Take a step back and ask yourself how you can make your site better for one random user.
One happy user leads to more happy users.