The immediate political indications of the Democrats losing what had been the Kennedy family seat for over half a century are obvious and have almost certainly been covered in-depth in other places, so I won't bother with that. Instead, I think attention ought to be drawn to certain interesting details from the results - and by 'interesting details', I of course mean Coakley's extremely poor showing in the old industrial towns* and in certain working class Boston suburbs.
First, and most dramatic of all, Coakley actually lost Lowell, one of New England's most iconic industrial cities, by about five points - an extraordinary result by any measure. While this result, perhaps the most shocking of a shocking (if not surprising) night, was not entirely typical, the pattern was. In Worcester, New Bedford, Fall River, Lynn and Holyoke, Coakley's margins were shockingly low. Coakley even lost Bristol County (one of the most working class in the entire eastern seaboard and usually a Democratic stronghold) by almost 10pts. One town in Bristol that voted for the Democrats hapless Gubernatorial candidate in 2002 with 60% of the vote actually voted for Brown.
The same pattern held in and around Boston; Coakley's margins in some working class suburbs (such as Everett) were embarrassingly low, while she was beaten in places like Revere and Quincy. She also appears to have done extremely poorly in South Boston, although I don't have any figures at the moment.
Although this was a by-election and although Coakley was a laughably bad candidate, these patterns should worry the Democratic Party.
*Mostly mill towns and so on. Massachusetts used to have a big textile industry and can be compared in certain respects (though not others) with Lancashire.