Finally, because there are only 33 or 34 Senate seats (depending upon the cycle) who are up for election (37 this year because of specials in Delaware, Illinois, West Virginia, and New York) Senate challengers of any credibility are "in the game" from primary night onward.
With 435 House races, voters may never even see the name of a House challenger until they pull the curtain behind them in the voting booth and look at their choices.
As the scene shifts to 2012, the Democrats will have 21 seats to defend of the 33 to be contested. Maybe defending more seats won't mean anything, but I think it will.
My best guess is Republicans will pick up eight Senate seats and go into the 112th Congress at 49-51. I also think the GOP will pick up about 50 seats for a majority of 229-206.
Find me someone who predicted that 18 months ago.