I've made it twice. 1st was extract and I just brewed the all grain version last weekend. I added 1 lb of light brown sugar at flameout the first batch and it came out fantastic! Gave it a little kick up to 6.2% ABV. I did the same thing on my last batch as well, but scaled down the brown sugar just a bit since I now use Beersmith and could dial in exactly what I wanted to achieve. This time I added 10.4 oz of brown sugar 5 mins before flameout. This is my favorite brew so far.
Primary#1: Sam Adams Old Fezziwig Christmas Ale
Primary#2: Robust Porter
Primary #3: Currently Empty
Bottle Conditioning: Pete's Golden APA, Burt's IPA
Kegged: Pete's Cream Ale
Drinking: Bells Two-Hearted IPA Clone, Janet's Brown Ale, Spotted Dog Brown Ale, BierMunchers Cream of 3 Crops, Chocolate Milk Stout, Oatmeal Vanilla Stout
On Deck: Chocolate Milk Stout