The big killer is variation in ping, not the actual ping itself. If you play at 150 every day your brain gets used to it and makes slight compensations. you will lead people a little more without even realizing it, for example.
The problem comes in when you play at a low level, say 25-35 all the time then jump to a server with a 150 ping. You will be shooting at ghosts. Those 125 milliseconds make all the difference
I have even seen the difference from 30 to 50. My ping is usually around 35 and I do ok, but when my connection is a little laggy and jumps up to 50-60 (thanks for not giving a fuck about that Comcast, by the way) it takes me about 4-5 rounds to get used to the new speed and the same in reverse when all the grannies on my street stop d/l photos from their damn grandkids