Before I get to the actual rating though, I'll explain what makes Happy Ending an "Imperial" Stout. The main thing is a higher alcohol content than is usual for a stout: A traditional stout like Guinness comes in at 6% alcohol by volume whereas Happy Ending is 9%. The extra alcohol adds tons of interesting flavor notes to the normally dry, almost light stout. The practice of adding extra alcohol to beer started when British merchant ships discovered that they could get a longer shelf life out of higher alcohol by volume beers- during long trips from Britain to British troops in India, Russia, or other countries, a longer shelf life was essential. So anytime you hear of an "Imperial" Pale Ale, an "Imperial" Pilsner, or in our case an Imperial Stout, you know it has a higher than normal ABV (and it probably tastes spicier, bigger, and more complex).
Happy Ending is, as I said earlier, an Imperial Stout and, true to the genre, its balanced nicely between spicy fruit/floral notes and robust chocolate roundness. The first tastes of Happy Ending are bright and floral but the flavor quickly shifts to a more smoky, robust flavor. Some people say its a chocolate taste, some say coffee; I myself tend to lean towards chocolate. Either way, it moves from the robust middle flavor to a flatter malt taste at the finish (despite what the name would have you believe!). For a high gravity beer (any beer over 7% ABV) its surprisingly drinkable.
Anybody who enjoys this beer may also enjoy Terrapin's India Brown Ale (which is only available on draft now, though Terrapin may be bottling it soon), Guinness Stout, or any Oatmeal Stout.
You can find Happy Ending at Total Wine in Kennesaw (any reputable package store will order it for you if you don't live around Kennesaw) for $1.79/bottle or $9.99/six-pack.
I'm giving Sweetwater Happy Ending a 4/5. Its a flat-out tasty beer that is complex and yet still very smooth. It smells great, has a deep, almost black brown color, and leaves a nice lingering taste after each drink. The only thing that keeps it from a being a 5 is that the end notes are a little flat and, in the interest of full disclosure, stouts aren't my favorite style to begin with.
Cheers!