I think its sort of the grass is always greener effect. The car needs constant attention, and really basic stuff like sensors, seals and rubber bits cost too much. A basic servicing seems to cost a ton.
Then however you compare it to what else you might buy and you realize anything else that drives as well and a great many things that drive way worse and are more of a pain in the ass on maintenance.
Once I came to terms with the fact that this car needs to visit the local BMW doctor every 3 months or so to keep it running the way it should and budgeted accordingly, I have been much happier with it.