Ah, the greased taper question
There seems to be no consensus on this one! If you put any on, it's a tiny amount, just a smear onto the tapers.
When Chris Bell of Highpath sent back some cranks he had modified for me, I noticed that he had put a little blob of grease onto the tapers. Personally I'm prepared to trust his knowledge.
I generally use copperslip on the tapers and also the crank bolts. The whole thing gets regularly sloshed with salty water, so I think it's a good idea to stop it all corroding together.
Ride it or milk it!