Before you think this is rumor or just random neigh saying, the news comes right from the Ubisoft blog. If you want to save yourself a bit of time, the short version for the delay is that Watch Dogs needs more 'polish' and 'fine tuning'. Usually this reads that the QA department found too many game breaking bugs and glitches and the development team needs to rework major and minor points of the game.
As I said, I have been looking forward to getting my hands on Watch Dogs since I first saw it presented oh so long ago. As with any delay for the reason given though I think it will be worth the wait. You will hear this about a hundred times over the internet today lone, but I'd rather wait for quality instead of having a disappointment of a game shipped sooner. I just hope that it will be early spring and not late spring but if I have to wait to save on headaches during gameplay, I'll have to deal. It's not like I won't have a plethora of games to play while waiting anyways.