Whenever a mouse mat thread comes up, I'm sure that the majority of the responses overall (i.e. on CS related sites) is the Steelpad S&S.
I've got a S&S, and used this one for at least 3 years - even after the top surface 'wears' so there is less friction it is so very gradual that your playing style adapts to it, it doesn't get that dirty either and it is no way as cold as an Icemat would be.
I've tried the following mousemats and always came back to my S&S -
func 1030 -> S&S
S&S -> QPad
S&S -> Steelpad 5L (back to S&S)
S&S -> new S&S (back to old one which was nicely worn - new one felt so rough in comparison)
S&S -> Razer Pro 1.6 (white mousepad) --> back to old S&S
So I'd say get an S&S, although I'm tempted to try the new Steelpad SX at some point.