to add to an already awesome thread, Rockstar seem to be introducing stealth patches to heists on a regular basis, patching out known exploits (while leaving others in, probably because those are too hard to remove).
for example, we've been having a lot of trouble with jets in the Prison Break finale. they don't go in circles anymore if you follow them in the Velum, they turn towards the military base to the West and just fly towards the end of the map, so following a jet will probably get you killed (either by base defenses or by hitting the invisible wall at the map's edge). we do sometimes get lucky, but most of the time it's safer to use the Buzzard to blow these jets out of the sky (if you're using your Kuruma inside the prison yard you don't need the Buzzard to help you anyway).
the other thing I've recently noticed is that if you are the sole runner to the bikes during the Pacific Standard finale, almost no cops spawn after you jump the second fence (and not a single helicopter). I don't know if it's a bug or if can be reproduced 100% of the time, but it definitely makes the whole mission a breeze.