Just did it and WOW
I had my 2008 135i reflashed remotely. The car is an entirely different animal now. The transmission no longer bucks, which it always did off the line when it was cold. Throttle response seems sharper, and overall the shifting is much, much quicker.
You need a 32bit laptop and a BMW cable to do flash it. If anyone wants to use my setup in the GTA toss me a PM.
For those that don't know what im talking about here's a video of someone that reflashed it: