I couldn't tell much difference between the stock mat on my Thorens 160, and a felt mat. But yesterday I slapped on an old Angstrom Ultimat and WOW! Tighter sound, more differentiation between instruments, nice liquid highs, and much less static noise (it is supposed to have anti-static properties).
There isn't much info available on the Ultimat. It is late 70s/early80s, and is apparently similar to a Platter Matter (unfamiliar with this mat). It is a smooth rubber, not the notched, ridged rubber stock Thorens mat style. I would recommend finding a similar mat to try. If you like liquid highs on your records.