As I said earlier, after a few attempts I found I liked mouse-drag alot better than p&c. I think I was put off at first in the same way I was initially put off using mouse for FPSes and third-person action games: hard to use initially, but easy to master. I avoided using the mouse until I realised that I needed to use it to be any good at Max Payne, and after a day I realised that I could not go back to the keyboard.
In a way, I feel the keyboard controls actually hinder learning the drag method, as it gives players an easy way out that isn't actually easier, when if they stuck with it they might get used to it. Then again, some people might not be able to get used to it (like me with gamepads, hideous things), so maybe not.
It is interesting to see that there seems to be a fairly even split between keyboard, mouse and combination, with combination only lagging a little bit relatively speaking.