I had a hardcore mead/beer maker convince me to start adding honey approximately 72 hours after fermentation has begun. So far, three batches, no problems.
Advantages: Lots of honey aroma/flavor, steady stream of fermentables for the yeast, some alcohol will be present to kill off some nasties by that point.
Disadvantages: Maybe it could infect your beer. Of course, this guy who starts at least 1 batch of mead per week has never had a problem using unpasteurized honey in either beer or mead, and he says he's never heard of anyone having a problem either. Of course, meads were made for millennia before we ever learned about pasteurization and the benefits of boiling. But, with that said, I suppose it could be a problem in your batch. Personally though, the more I think about it, I'm just not -that- worried.
I say add it to your primary.