The Keystone pipeline is a purely political controversy. It doesn't much matter, economically, whether it happens or not — albeit, some environmental concerns may have some validity. If constructed, the general professional perspective is that it will generate between 35 and 50 permanent jobs. Here and there, some pipeslingers will have work for a year or two, but given current crude oil prices, constructing it is not worth the trouble.
Mary Landrieu, stuck in a probably doomed run-off election, will keep pushing it. Obama can veto it without losing any support, and maybe gain a little more support from the greenies. The big problem for Keystone is that oil prices have dropped so low that tar sands oil just can't compete. Tar sands oil is just too expensive.
Clearly, Obama should use his veto, unless he's still idiotically trying for "across-the-aisle" reconciliation. That won't happen, so let him screw them every way he can. Payback's a bitch.