Your computer can only render images at around 60 frames per second, as that is the screen refresh rate. Basically, every time your computer hits 60 frames, it will refresh the screen. If you have a high fps just looking at the ground, that doesn't really mean anything Its just that IF your computer refreshed that fast, or IF you could actually notice that. You can't really notice about 24, I think (might be 30, will have to check that). But a FPS over 60 is just basically compensation. Basically, if you have a high FPS that means that you have a lesser likelihood to go bellow a undesired FPS, i.e 60. All of that aside;
I get a a steady FPS of 200, with FPS drops to ~175 FPS occasionaly when things happen (creepers exploding, etc) this is when walking around and doing stuff, I run Optifine Ultra with max graphics in fullscreen on 2 monitors.... so ya.
