I bought my kegerator for the expressed purpose of drinking stout as I do not particularly care for many ales or pilsners. I run Murphy's Irish Stout exclusively in my kegerator, and although running it through a 'normal' faucet and pushing with CO2 (at your normal 8-12lbs) is possible, nothing compares to actually converting your draught system into a 'stout' system. After running a 50L keg through with the CO2 and 'normal' faucet, I made the upgrade to the 'stout' faucet and mixed blend gas and ran another barrel through. The difference is well worth the cost if you are as anal with your beer as I am with mine.
The cost is rather high, I had to buy the special faucet for ~$90 (it is brass - you may find a cheaper one), and I depressurized the CO2 and replaced with a mixed blend of 75%Nitrogen/25%CO2. The difference is remarkable, and gives you that perfect, rich, cascading head that everyone raves about. Also, depending on your line length and line diameter, you need to determine at what pressure to set the regulator at, as stout needs to be HIGH to force it through the special faucet - it has TINY holes and a plastic 'spinner' which is what agitates the liquid as it is being poured (my calculations came to 32lbs, and it pours perfectly). There is an easy way to determine this pressure using a formula - I can't find it right this second - but there are multiple resources online for it.
I was able to convince my local gas supply store to charge my 5lb tank with the blend, but you may not be so lucky. Officially, you need a stronger tank to hold Nitrogen, and most companies wouldn't consider putting Nitrogen in a CO2 rated tank.
So I got away cheap with $90 for the upgrade, but officially you will also need a different tank for mixed blend gas containing mostly Nitrogen as well as the adapter from that special tank to your regulator.
I just finished purchasing all the equipment I need for my first AG batch of stout and plan on brewing tomorrow morning. I will be sure to post some pics of the process and let you all know how it turns out!
Wish me luck!