instantly - a couple hours of hostile manipulation designed to screw you over
It took me 2.5 hours to buy my truck where the price had been determined before I walked in and I had a check in hand. That's after the research to get a price upon walk-in ($6000 less than on the sticker). The process of walking in and looking at prices that everyone knows aren't real and negotiating with someone who is lying to you is beyond tiresome.
I think internet sales have changed that, though. We got our last car - I did the looking and pricing out online beforehand. We spend about 30 minutes in the dealership when we went to buy it.
They were very straight forward online - all in print in e-mail. You want x car, in y trim level, it costs $z. Are you financing or not?
The only thing they tried to sell us was a maintenance package that, if we lived closer than 3 hours away, actually was a good deal for the cost.
