obviously you've never played the same game and maxed the fps at 100 and then 30, the difference is huge, the entire game feels completely different.
Now, as for thinking there are no monitors in production that do 100hz refresh rate, erm? yeah there are. The best range by far are the Samsung Syncmaster. My screen gives me 100hz refresh rate at 800x600, and 120hz refresh rate at 640x480.
Now if this guy wants to play games competitively, seeing someones head pop out is the least of his worries. First of all he needs to consider aim, and then gamesense, after that is where hardware really kicks in, being able to see a massive head with a massive crosshair defeats the point, plus recoil really means that having a big screen won't help. Furthermore, bullet registration, the movement of the mouse, and the recoil on the crosshair (if there is recoil) is all related to your fps.
So no, it's not about getting a minimum 30 fps because that's all your eyes can see, its hugely important to get good refresh rates, and no professional gamers would ever dream of using that behemoth of a monitor