It does indeed matter - a great deal.
1) In the last half of the year Gillard was gaining momentum. They were starting to more clearly articulate their narrative and achievements. They were testing out their language for the election year and it sounded good. The rogue Newspoll which showed Labor gaining ground was very important because it gave substance to noise which had gathered around Labor that they were competitive. For a few week after Christmas the dynamic was shifting, and it was favoring Labor. Team that. by the way, with the some money for western Sydney... Then, all of a sudden the media goes wild and you get this show. You get a week long discussion on Gillards lack of judgement and how Crossin was 'knifed'. This was very important because yet again Labor has shot themselves in the foot and naturally at the same time has stalled them. Also... speaking of poor political judgement, Gillard had to do a news conference, this only amplified the problem - this could of been done much more quietly.
2) The fact that Crossin was not alerted to the Nova raid plays into the libs message of 'you can't trust this PM'. If you think we won't hear this again then you're a mug. There is already a rusted on opinion that the PM is slippery - regardless of what you think her polices are like.
3) I don't really mind the 3rd point but ... It shows contempt for the NT Labor Branch, the sitting Senator and shows a loss of faith in the 'proper' Labor process. However I'm not so concerned about this as both sides drop 'star' candidates in.
4) Simply put, Nova is a novice. At her press conference(s) she was nervous and bogged down by questions re: nature the pick. She should of simply said that its about policy and all the good stuff and start ti use the national media to sound out her beliefs.... It was great air time, but her incipience wasted that.
Our friend AJP Taylor might say that the Nova decision has 'Put the wind in the Coalitions sails'