I think the Rangers will have trouble with big, physical teams, and especially teams with big mobile defensemen. Of course, most teams have trouble against those kind of teams, and there aren't that many who have all of those things and are good.
But that is why Boston will always be tough...their D is good enough that it becomes harder for the Rangers to get their cycle going and maintain possession like they do against teams like the Avs who have weak defensemen who don't move the puck well. The Rangers smaller forwards can't always win all the battles against the big mobile defensemen like they can against small mobile defensemen, or big slow defensemen.
Then big forwards who forecheck hard and are tough to take the puck away from make it hard to go back on offense...which isn't unusual but again it's tough when a team has both of the things I mentioned and the Rangers don't necessarily have a clear cut counter to all that other than just playing a perfect game and capitalizing on their chances.
Pittsburgh, you just gotta try to keep them from running wild with Malkin and Crosby and all that, I'd bet if you can manage to possess the puck more against them and put pressure on them in the defensive zone, Fleury will look mortal real quick.
Columbus actually scares me, I think they're a well constructed team now that plays a relentless game. Their D isn't amazing or anything but Bobrovsky can hold things down when the defense gets crazy. They can roll 4 lines and play physical and hold onto the puck well, they're a good team. If the Rangers can hold onto the 2nd spot, I'll bet you that Columbus ends up in 3rd. Would be a tough first round matchup