I've gotten pretty good at FTL, but haven't beaten the final boss all that much. Yeah, it IS an exercise in frustration, on purpose! It's not like a typical modern game, where so long as you put your hours in, you should expect to win.
One reviewer said something to the effect that it's not so much about winning the game, but seeing how far you can get before you die. I find this true a lot. Incidentally, the reviewer liked the game.
Certain strategies improve your odds of surviving a LOT. Like even a Defense 1 drone can save you from tons of missile damage, lowering the need for repair, thus freeing up scrap for upgrades.