The Big Dig was also a horrific pain when it was going on. (Oh, and Boston traffic is also still horrific.) Nonetheless, once done, it was a nice transfer payment to Boston that the Speaker of the House (Tip O'Neill) arranged for the rest of the country to make that reversed the also horrifying neighborhood-splitting overhead highway decision. Boston is better for it.
The Big Dig almost certainly resulted in less bad traffic than would have existed otherwise--and eliminated some really painful traffic patterns like getting to the airport. But elevated 93 which cut off the North End from downtown was just a blight generally even if it took years to get the greenway plan approved.
I guess SF had the "advantage" of an earthquake to eliminate its issue.
