I did a coffee stout recently. A sweet espresso stout actually (stout + lactose + espresso). It turned out amazingly well.
I definitely recommend cold-brewed coffee as an addition for your coffee flavor. It is really easy.
Use coarse ground coffee (ask for french press or coarser grind when you buy your coffee), stir coffee grounds and cold water into a slurry, put in the fridge for a day or two, decant and filter the resulting coffee, add to beer.
I used 4 oz of espresso and about 1 liter of water in my erlenmeyer flask for 2 days, then decanted the coffee thru a cone filter placed in a funnel right into my carboy. This was for a 5 gallon batch.
Remember, with coffee freshness matters -buy your coffee somewhere that roasts their own. Also any off taste in the water you use will be obvious in the coffee extract you produce -buy filtered water if your tap water isn't perfect.
The big advantage of cold brewed coffee is the lack of bitterness. If you have never tried it, and have only ever had drip-brewed coffee, it is very different.