I've been using Redline oils in my 135i for years now. I have a manual trans so I have been using RL's ATF D4 in my manual trans and their 75w140 gear oil in my diff. I now am using Redline's MTL in my manual trans. I recently saw this cool video on RL...
///Drive - Dispelling Myths About Oil -- /ENGINEERED...
http://www.1addicts.com/forums/showthread.php?t=1330260
I am a firm believer in changing ALL the fluids in my car. I first changed my diff oil at 28K kms and the diff oil was really dark and nasty. I had to use a suction pump to remove the oil oil. I first used BMW Castrol in my diff and later have changed over to Redline gear oil.
DIY: manual transmission and diff fluid change
http://www.1addicts.com/forums/showthread.php?t=409293
Not a whole lot of guys have changed their DCT fluid on 1Addicts. I think most guys with an e9x M3 just use the factory DCT fluid from ZF/BMW. From what I've read the trans is the same unit except for the internal valve body from M3 to 1er dct.
Another good source for automatic fluids and parts is T
he California Transmission Supply Company...
http://www.thectsc.com/
Dack