I've actually found that the car buying experience is not that bad at a dealership, but the service/parts department is not something worth dealing with unless

I've actually found that the car buying experience is not that bad at a dealership, but the service/parts department is not something worth dealing with unless you really have to. At this point; the dealers know that you know what the invoice price or KBB value of a car is, and what kind of loan rate you can get elsewhere. They might want to sell you a warranty or the like, but at that point you've already negotiated the price of the car, know your loan rate, and can just say no to the extras and move on.