Well i'm not saying its hard, and it is way easier then with a mouse. But it feels very different then drawing on paper. For one, when you draw on paper, you can always see your hand/pencil and see where its going with the line. With a tablet, your eyes are always on the screen, while your hand is moving on the tablet. So you can only sort of guess where your hand will go next. And secondly, the size of the tablet is usually not the same as the size of the monitor. So the stroke you make on the tablet is not the same size as the one you see on screen. These things throw off your visual sense and like JQP said, its more like drawing by feel.

Some people can manage with this and some cant. Only way to know is to try it yourself and see.

Quote - I'd agree with this except, what's the alternative.  You have to learn to draw by feel with a tablet, and that's not easy, but in any case it's far better than a mouse and I know of nothing better.

The Cintiqs are the alternative, but given their price not a solution for everyone. Hopefully they will become cheaper in the future, cause they are a dream to use over a normal tablet.