If Democrats get the hat-trick in the Senate over the next month with wins in MN, AK, and the special election in GA, there's another aspect to consider.
If Democrats get their filibuster-proof majority of 60 seats, we will see the fractured Republican Party heal itself immediately as their party leadership forces their caucus to vote NO on every Democratic bill and to attempt to filibuster everything. In response, the Senate Democrats will have to stay united in order to win, leaving a progressive agenda held captive by weak-kneed Democrats or, even worse, by craven D's like Lieberman who want to hold legislation hostage and extract concessions from the White House.
That will leave a stain on Obama's presidency as all of his agenda will be a complete party-line vote with no show of the bipartisanship that Obama promised and that voters want.
OTOH, coming up just short on the 60 votes leaves moderate Republicans some wiggle room to defy their leadership on a lockstep party-line vote. Mods like Snowe, Specter, Collins, etc. will be able to retain their independent (dare I say, "maverick") reputations as President Obama courts them hard for their support.
There are pitfalls to getting a filibuster-proof majority and they are worth considering as votes are recounted and special elections are arranged over the next month.