I've been using the Razer eXactmat for a while now, and it seriously makes a difference, specially on high dpi settings.
Simple test I did once for a mate ( as he allways argued on this). I had him play COD5 with a bolt action rifle with my mouse and a normal mousepad, an uprated but still entry level hardpad and just on the table. then I switched to my razer pad (without telling him which one is whitch) he instantly shot better, he commented he was much more accurate, got onto other players quicker and it just felt better, then I told him it was on the Razer, he was cheezed off cause I had proven him wrong. Next day he had one of his own