This isn't a dig at the Leafs, but I think Leafs fans sometimes overestimate the team's place in the collective consciousness of the other fanbases. I don't spend a lot of time thinking about the Leafs and don't feel a strong rivalry with them. They don't have any dirty or unlikable players, and haven't beaten my team in the postseason or won enough Cups recently for me to develop a dislike towards them, no offense intended. At the moment they're just a young, talented yet unproven team that may or may not fulfill their potential to win a Cup or two.
Maybe it's different between other Canadian teams or a historic rival like Boston, but I'd wager the majority of American fanbases hold a relatively neutral view towards Toronto, despite the frequent insistence on this site that everyone hates the franchise.