I never used it and all my planes flew well. I think the benefits (I may be wrong) are that it seals the air from pasing between the tail surface and the control surface. When you pull back on the elevator, it sorta makes an undercambered airfoil, only inverted. This makes "lift" on the top, or a higher pressure, and a low pressure at the bottom, which pushes the tail down, raising the nose. The tape just keeps the high pressure from bleeding through the gap to the other side. This is supposed to make the controls more responsive. I think the effects a minimal at best, and probably not noticable by a beginner (like me ), especially on a trainer.

Another benefit on faster planes is that it stops the surfaces from fluttering. On a fast sport plane or a racer, sealing a hinge line can stop flutter that would otherwise rip the surface off and destroy the plane!