Heli-coil questions

So does anyone use heli-coils here, or are they(heli-coils) a cheap/quick (half-a$$) way to do something? From what i have seen they work pretty well, and some companies, say they are even better than the old threaded hole?(please let me know why they say this). I have seen friends/family use them on blocks with stripped head bolt threads, and they've held up so far. So what i am wanting to know is , is it worth heli-coiling something? Now the reason i want to know is that my heads bolt holes for the exh. Manifolds, have stripped. I fixed two, and one just went all wrong for me. The tap broke inside the hole, i drilled the tap out, and the hole was enlarged (big time). So i have since drilled it out to 29/64 ths, tapped it for 7/16" threads, and have installed a stainless heli-coil. Will it leak is a major concern that hit me? I also used high-temp red rtv on the threads of the heli-coil, and am planning on rtv'ing the bolt as well. Will this hold up, or will i be pulling the head again in the near future?