I expect the S2 isn't that much different from the TC, and for me it depends on the time of year. If the sun is high (summertime) then they're not needed but about now, when the sun is low no matter what time of day, they are useful. Also when driving on wet roads into the sun, they do help in reducing the glare just like on any car.
I ran my car without them just after doing the headlining but since then I covered them in the same material and re-fitted.
Brian