So what's the deal with ATF?

I have heard it all and I am a bit confused on this matter.

1- Dealer says don't change it unless there is a problem.

2- Jim-Bob says flush the whole darn thing clean out at 1000psi

3- Sir Lancelot says just drain some and refill, repeat after 2000k

4- Master mechIII says use synthetic only

5- Master mech IV says the opposite

7- I say, ?.....What is the real deal then????