My 330d has the same gearbox as your car and same engine, I have done software and have been driving her hard all the time, the gearbox has never given any issues, my turbo has poped but that isnt due to software, thats due to the fact that the turbo lived a long healthy life and was time to say cheers!
My car was making 576nm then I got stage 3 software which made a massive increase in power so I am guessing it was making well over 600nm ATW and my gearbox never gave any shit!
From the research I have done on the net I have found that the people who have opened these gearboxes up to replace the lubricants are the people that have had shit with the boxes as they are supposed to have a lifetime lubricant inside and BMW warn to not open or change that lubricant, but their are also people that have done software and the gearbox has broken, but on the other hand people have had these boxes break with no software and no mods, so in my opinion you either have a gearbox thats going to break or you don't its luck of the draw.
I think if you drive the car like a doos then it will break, like holding the break and pressing the accelerator to make the wheels spin or to get a good launch is a good way to fark up the gear box, or reversing out of a parking fast and before the car has come to a stop popping it into drive will also fark the gearbox up, or hamering the car when its cold can also stuff it up because the gearbox is also cold and will also suffer under those conditions.
Just my opinion.
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