weapons as implements

[Eldorian]

A pact blade is simply a light blade, so it is simply a magic weapon that can function as a implement. So the moment you use the pact blade (dagger example) in a melee attack you only gain the bonusses as if using a magic weapon, and not as a implement..

Yeah, I know what a pact blade is.

Oops, I forget to mention the nimble blade feature.

That makes slightly more sense. What do you mean about opportunity attacks?

If you mean, "Does a warlock using a pact blade who has the nimble blade feat get an additional +1 to hit when he has combat advantage when casting spells?" then the answer is yes, as would a sorcerer with the same feat and a dagger implement.