Left Hand Brewing Company from Longmont, Colorado, is one of my favorites. Their Fade to Black Volume 3 and their "normal" Milk Stout are two of their products I particularly enjoy. Milk Stout Nitro takes the regular Left Hand Milk Stout to another level.
The "Nitro" in the name comes from the use of nitrogen to help "carbonate" the beer. Nitrogen causes the beer to have a very thick, durable head that lasts pretty much for the life of the serving. It also adds a creamy milkshake-like mouthfeel to it.
When you combine the chocolate flavor of this Milk Stout with the creaminess of nitrogen, you get something like a dark chocolate milkshake with alcohol in it. The milk sugar component of the stout is made a touch sweeter by the nitrogen, which effectively balances the natural bitterness of the hops in the beer. For me, a chocolate and beer fanatic, it's practically a perfect beer.
Beer Advocate rates the regular version of Left Hand Milk Stout 88/100 or "good". There is no specific rating for the Nitro version, but I have to think it would be above 90.
I've seen this at a number of local retailers, including Kenny Road Market, Weilands, and The Andersons General Store.
My rating: 10/10