i noticed something. when i use bagginsbill's  ENV_sphere and if i turn off raytracing then it renders very long.
so basicly if i make the ENV_sphere invisible for raytracing then it renders longer.
of course when AO is turned on. so i made some more tests. if i make a ball and make it invisible for raytracing and turn on AO it will also render longer.  if i turn raytracing on the ball on it renders faster

is this normal?