Political reaction to the President’s appointments today was swift. 

Senator Mike Enzi (R-Wyo.), Ranking Member on the Senate Health, Education, Labor and Pensions (HELP) Committee, said he was "extremely disappointed to see President Obama recess appoint new members to the National Labor Relations Board (NLRB) and avoid the Constitutionally mandated Senate confirmation process."  In a news release, Sen. Enzi further noted:  

Two of the three nominees were submitted to the Senate on December 15 and the Senate adjourned for the year on December 16, which provided the Senate with only one day to consider and review these nominations. To date, neither of the Democrat nominees has filed the required committee application…

CNN has catalogued the reactions of "Republicans furious over recess appointments" at its 1600 Report blog. 

On the other hand, the President’s action was praised by AFL-CIO President Richard Trumka:

We commend the president for exercising his constitutional authority to ensure that crucially important agencies protecting workers and consumers are not shut down by Republican obstructionism.  Working families and consumers should not pay the price for political ploys that have repeatedly undercut the enforcement of rules against Wall Street abuses and the rights of working people.

Likewise, the move was celebrated and defended by Travis Waldron at ThinkProgress:

Republicans have shown outrage at Obama for using his recess appointment powers with Consumer Financial Protection Bureau director Richard Cordray, and similar outrage is likely to follow the news of the NLRB appointments. But the past three Republican presidents also made recess appointments to the NLRB. Ronald Reagan and George H.W. Bush each made three recess appointments to the NLRB, while George W. Bush made seven such appointments.

LaborUnionReport noted months ago, however, that when President George W. Bush (R) sought to make recess appointments to the National Labor Relations Board, Democrats in Congress, with the vocal support of organized labor, employed the very same "pro forma session" tactics currently being used by the Republicans.   

Not every one analyzing the President’s appointments today so casually overlooks the fact that the Senate was in pro forma session.  At The New Republic, despite general support for what the President hopes to accomplish, Timothy Noah questions the constitutionality of the President’s actions:

The trouble is that the Senate isn’t in recess. For complicated reasons the Republicans have the ability to prevent the Senate from going into recess, and they have done so in order to maximize the difficulty of Obama making recess appointments. The White House maintains that keeping the Senate in pro forma session is a stupid gimmick, which is certainly true. It further maintains that because it is a stupid gimmick, that gives the president the right to act as though the Senate were in recess. That’s the part I have trouble following.

His updates include links to some additional contrary views.

Looks like we’ve found our first big labor law issue of 2012.  Stay tuned…..