My experience with Mission Hills Nissan has been so-so. The sales person I worked with was a nice guy, but was not very knowledgeable about EVs. I didn't buy the car from him, not for that reason but because we couldn't negotiate a fair price.
I also tried their service department since it's the closest dealership to me. I had to go in twice to get the "grabby brakes" fix done. The first time, the service rep didn't know anything about the problem, couldn't find a service bulletin for the problem, and never saw an abnormal problem with the brakes of any of the LEAFs in the shop (could be that there haven't been many in the shop). The second time I brought in a copy of the service bulletin and asked him to apply it. Fortunately, the mechanic followed the service bulletin correctly and fixed the problem the first time. I also had them install the front license plate frame since the instructions made me a little nervous. They did a good job on installing the frame.
I'm not too concerned with using them at this point for service. The car seems to be pretty low maintenance, and this forum has helped out a lot with known issues, such as the brakes issues I mentioned. If I run into something serious, I may take it over to the dealer in Downtown LA, as they seem to get a lot of good feedback, but it's a pain for me to get down there.