Can any of you more knowledgable types tell me what effect the old/new ball has on a spinner? I know the new ball is much better for the pacemen but is it any particular disadvantage for spinners? Does it have any particular effect on the spinners?
It's vital to be able to grip the ball as a spinner, and a ball with some rough on it is much easier to grip. There are some spinners who are comfortable with a new ball, but not many. Swann is one of them. There will be many more in the coming years because of the trend for spinners to take the new ball in 20/20 and other forms of one day cricket.
The main reason spinners don't bowl with it however is that it's not going to make them turn it any more, whereas it will almost certainly push through and swing for seamers.