Their secondary is mortal but the Colts' front 7 are actually very solid. I expect them to put a lot of pressure on Big Ben and force some mistakes. I they can force Ben to make one of those boneheaded throws of his and force turnovers, they're looking good.
The Colts have both a good passing attack and an underrated run game. Taylor looks very good and Hines is their version of James White and seems to have broken out. They've got good targets in Hilton and Pittman and some nice second rank WRs like Zack Pascal and Marcus Johnson to fill out depth in the receiver corps. Their offense is fairly well balanced and their defense, despite the leaky secondary, isn't to be laughed at. I'd say it's about 60-40 in favor of the Colts vs Pittsburgh, possibly more given the X factors affecting the Steelers right now.
And yes, they are being looked past by a lot of people right now. Irsay's an idiot but that doesn't mean he's 100% wrong at all times. I think the biggest thing causin people to be skeptical of the Colts is Rivers' own track record of not getting it done when it really matters. If they bomb out early and/or don't make the playoffs, it's probably gonna be on Phillip Rivers in some way.