Service wise they were fantastic. Very friendly and helpful, and even called me a taxi to get into Konstanz while they did the work. They are BMW specialists and I can only assume the work they did was good. The garage was full of Swiss plated cars.

My only gripe was the cost. I just had the basic oil+filter service and the bill was 300 euros. No other work was done. This was the first time I have serviced the car, so I have nothing to compare it against, but this seems a lot. They gave me a receipt to claim my tax back on the border though (but I didn't bother claiming as it was only 20 eur).

In short, if someone tells me that is a good price, and much cheaper than in Switzerland, I would definitely recommend them. Otherwise maybe not. A German at work recommended the bmw dealership in Waldshut.