I'm for national reciprocity, as I think it could be handled similar to how Driver's Licenses, and other licensing is concerned. Sure other states may have different rules and such, but they are honored from state to state. Simple question with a not so simple answer then is, 'If it has been done with those, why not with carry permits?
There are, as I see it, a few problems with comparing Federally-mandated national CCW reciprocity with driver's licenses. First and foremost, reciprocity of driver's licenses was reached through agreements between the states. Allowing the feds to mandate CCW licenses would be letting the camel's nose into the tent and I fear that fed interference with specific state CCW regulations would follow.
Secondly, while there are some minor variations, the basic traffic laws, driver's license requirements, and rules of the road in all states are fairly uniform. Someone familiar with the traffic laws of one state can drive in any other state with a fairly low risk of violating traffic laws unintentionally. Likewise, just about every new car being sold is legal to drive in every state. CCW regulations, on the other hand, vary widely. There are wide variations from state-to-state regarding requirements for obtaining a license, what type of gun may be carried, what type of ammunition may be carried, what type of magazine may be carried, the manner in which the gun may be carried, when/where carry is legal, and how one must interact with a police officer when carrying. Someone from a state like Indiana, which has very loose CCW regulations, could easily break the law without even knowing that they're doing so by carrying a gun with a so-called "high capacity magazine", carrying hollowpoints, carrying openly, carrying in an establishment that serves alcohol, or failing to inform a police officer that they're carrying because, while all of these things are perfectly legal in Indiana, there are other states where they are not.