I have never had a better experience in 40+ years of driving. My transmission is like new at a very nominal cost. I learned that this can be much more serious (costly!) if left to deteriorate - which it will.
My issue started years ago with my 2008 550i Msport. I am the original owner. The automatic tranny started bumping hard into first gear at a complete stop leaving the impression that you got tapped from behind. It was worse when cold.
I took the car to a well known NJ BMW dealership who has worked on the car since new. They then tried reprogramming the software / "adaptations" which effectively did nothing but cost money. I then did a lot of reading and saw ZF's recommendations were to replace the fluid at earlier intervals than where I was currently at 74,000 miles. Who knew?
BMW foolishly suggests lifetime fill on tranny fluid. I took the car back and requested the pan, filter and fluid be changed as per ZF. It didn't improve shifting but it did cost a lot more $$. They (BMW) simply refuse to do any work on the valve body or its components etc. BMW suggests replacement of tranny, valve body (mechatronics) or both at HUGE COSTS. They cannot or will not help with these problems so don't bother with the dealships.
Soon things started getting a bit worse in shifting from 1st, to 2nd and 2nd to 3rd and back etc.. Reverse was slow to connect as well. There was hesitation and a feeling that the tranny just did not know what to do at times. I even got a few hard slams into first gear if I accelerated hard. These are typical symptoms Mr M Car was very familiar with AND CAN FIX if they don't get left for too long. That is the key. I actually stopped using the car as often as a result. As things deteriorated I spoke with Don and Dwayne at Mr M Car in Farmingdale NJ. Don immediately drove the car and felt they knew what was wrong...but I foolishly waited and further reduced my 550 driving. I finally decided to put it in their hands after getting great service done perfectly and reasonably. They suggested replacing the rubber fluid seal connections between the mechatronics valve body unit and the tranny gear box, and replacing or topping off fluid after reviewing wear. I thought I'd need new valve body solenoids possibly as well (apps. $400+ if you can find them), but they did not feel that was needed, and advised against it based on it's driving characteristics which also proved correct when hooked up to the diagnostic equipment.
They suggested new seals would cure it, but also found that the fluid was not properly refilled after its trips to BMW, and was down nearly 3 quarts of transmission fluid! I was lucky not to have waited longer since doing so would've eventually destroyed the transmission - even if properly filled ($$$$). They've seen that too.
Mr M Car replaced the 6 sealing sleeves and topped up the fluid which is tricky and needs to be done during a short interval when the tranny fluid reaches a certain operating temperature - which I could never do. This was completed without fanfare in a day, was picked up and driven now for a week. This tranny is an automatic that has NEVER operated better than it does currently and the cost was extremely reasonable. Did I mention a new Mechatronics valve body cost $3,000 (rebuilt apps $900), and a new transmission is approximately what the car is currently worth. Moral: If you have bumps into first gear at a stop, or weird shifting - Don't wait! I was lucky. My only regret was missing out on the enjoyment of driving the car until having Mr M fix it.