Coffee spill on MacBook Pro Retina I spilled half a cup of coffee (Nescafé, whole milk, water, no sugar) on the keyboard of my MacBook Pro Retina 15'' (MacBookPro10,2, Early 2013)
Details that you can skip:
It happened almost 3 days ago (62 hours as of this post).
At the time of the incident the mac was powered on and in use.
I immediately:

unplugged the power cord,
forced a shut down (by pressing the power button for a few seconds),
turned it upside down, with the keyboard facing down and parallel to the floor,
tried to wipe it dry,
sworn a lot.

Before bringing it to the Apple store, I decided to wait a few days to let it dry and try to power it on again. After all, something similar happened years ago with an 2008 MacBook (white) and a glass of water, and after a few days of rest the mac recovered fully.
(If anyone is wondering, I even left it a day and a half in a plastic bag with a lot of rice)
However, now it's been almost three days and it still doesn't power on.
I gently removed the power button from the keyboard and it looks dry, although the contact under the rubber pin seems a bit dirty.
Question
Does anyone know what kind of damage should I expect? Is it possible that once completely dry it will work as usual?
In situation as you described, HDD could survive with high probability, but as MBP retina uses SSD instead there is a small, but chance to kill it. First steps to repair it is to disconnect the battery and disconnect the SSD. This is guarantee to prevent:
1) future information losses
2) future damage of logic board.  

What damages can you expect - generally, in these cases this is 50/50 game. Cleaning requires disassembly of the MacBook and wiping board with cleaning agent e.g. ethyl alcohol (96% concentrated). It is non-conductor, so then when macbook will be reassembled, it probably will work.
My friend had similar problem: water and MBP retina 13. And now his MBPr works OK, but only with power cord plugged in. I do not recommend connect it to power cord until it properly dried and cleaned (with alcohol).