Any team is capable of beating any other one in the playoffs. I think there are several teams built to beat the Pats, but they are in the NFC. The 49ers and Giants probably have the best shot.
I am not convinced anyone in the AFC are built to beat them. The Broncos may be a different team than when they first faced, but so are the Pats. The Broncos have yet to put up a strong performance against an elite team and pretty much lost to all of the ones they faced.
Still not sure the Steelers can beat the Pats. Other than the last time they met, Brady pretty much has their number.
The Pats have to be considered the favorite right now. Their offense can beat you several different ways and they can run on you as much as they can pass. Their defense isn't the 85 Bears, but significantly better than last year and seems to be improving.
Anyone can get hot in the playoffs (look at last year's Giants and the Jets in 2009). There is no dominant team right now that is a class above everyone else (although the Pats can make a strong case for that tomorrow night if they can beat the 49ers like they have other opponents recently). Even though I don't think any AFC team is built to beat the Pats, I wouldn't be shocked if one of them knock them out.