Working hours definitely make a difference with my entertainment informational site. Traffic peaks at 5:00 - 8:00 pst. When PST is getting off work and EST people still haven't gone to bed. Pretty consistent during working hours, and dead in the wee midnight-8am hours.
I notice hourly patterns that coincide with potential "break" times too.
Have not noticed any algo changes in terms of my site's traffic for the past couple days other than the usual site specific growth / decreases.