Would never ever ever ever have a dealership perform anything other than warrantee/recall work for me.
Working in a transmisison shop for about 9 months several years ago, heard all the horror stories.
When I bought my current car in 2003, VW dealership was unaware that the specs for my new car were synthetic oil.
On a car that was one of their top sellers.
I ASKED for synthetic oil, bacuase the sales guy (at a different dealership) had told me up front about the spec.
They gave me regular anyways.
When I commented on the $29.99 charge being a great deal for synth, they looked at me like I had two heads.
At least these guys were only incompetant.
The stories I've heard about dealer service depts indicate that a significant number a totally dishonest.
Things like charging for installing a rebuilt transmission, when all that was done was spraying the pan with noise deadening paint...
My advice:
If you have a garage, do oil changes and whatever other maintenance you can, yourself.
For everything else, find a shop that secializes in your make, and that is recommended by people who's opinion you respect.
Sure, there are honest and dishonest shops of all shapes and sizes, but I'd rather deal with shop owner that does some of the work himself, than a "department", especially since the dealerships around here generally charge higher rates and charge more for parts.