I know of a number of people who use non-OEM fluids in their engine, transmission, differential, and brake systems with no complications whatsoever. In fact, a few reported improved results with their manual transmissions when they switched fluids, which is something that can readily be felt. A friend of mine has had oil analysis done to his oils both OEM and aftermarket, and tells me that his reports show marked improvement on the non-OEM fluids. Just food for thought, though I personally don't blame anyone for wanting to stick with OEM fluids, peace of mind is invaluable.
"As I lay rubber down the street, I pray for traction I can keep. But If I spin and begin to slide, please dear God protect my ride! Amen." ― ONEBADWS6, LS1TECH.com Member