I'm not sure how I feel about this line of criticism of Harry Reid. At present, the Democratic party line is that the PBA ban was a bad law. He is, at present, the leader of the Democrats in the Senate. He was not leader of the Democrats in the Senate when he voted for the law (though the then-leader voted for it, interestingly enough). Thus, in addition to the possibility that he simply changed his mind (four years have passed), there is also the possibility that he feels obligated in his role as spokesman for his party to defend his party's position, in a way that he did not four years ago feel obligated in his role as a rank and file senator to vote against a bill which his own party's leader was voting for.
Of course, I don't know all of his motivations. But successful members of congress really can't avoid making compromises (that's why they make rotten presidential candidates; their compromises are quite embarrassing on the presidential campaign trail). I don't see why anyone who agrees with Reid's present statements should be jumping on him now for being inconsistent with his past positions; surely we should be celebrating that he's taking a stand on the right side now.