I can attest to Mason being a head case. When he's on he's on, but when he's off... whew... let's just say you're well served to have a good back up.
And I love Columbus (as you know), but as well as they're playing right now, they lack playoff experience and (I believe) aren't ready to go far into the playoffs, but I think they'll make a good push too. I'd love to see if they can bottle what they're doing now.
San Jose though... I don't know. They're a really solid team, but I always joke that Joe Thornton will never win a Stanley Cup and after last year... I think I may be right. I don't know what it is about Thornton and the Sharks, but as good as they are, they just don't have that killer instinct.
Montreal is good, but there's something a little off with them. They'd started the season with something like nine wins and then the Jackets beat em 10-0. Something just doesn't compute there. I have a feeling that while they're good, they're a bit lucky, too. :D
I don't think you have much to worry about with the Rangers though. They apparently don't wanna play the forecheck. I haven't watched them much this season, but a friend of mine who does watch em said they practically don't forecheck at all and when they do, it's usually one guy on the forecheck and four stationed around the blueline. If that's true, then I don't see them doing anything in the playoffs at all.
I feel like Chicago is always a threat, I agree that Philly could be a tough. I think St. Louis might surprise some people. I thought they looked pretty good last season.