Deacon Brodies on the Royal Mile has a good vibe to it, and a great selection of cask ales. I enjoyed a Rev. James by Brains Brewery of Cardiff. Funny, I was just thinking about Wales on my way in. The beer, like all Brains products, is very good. According to their website, "the beer is named after one of the original owners of Buckley Brewery, the Rev. James Buckley, a business man with two conflicting roles – saving souls and satisfying thirsts." I'm not sure I see a conflict there. However, the pub's namesake, Deacon William Brodie himself led a truly conflicted life, and was the inspiration for the Robert Louis Stevenson story The Strange Case of Dr. Jekyll and Mr. Hyde.
Despite being right in the middle of the tourist action, this pub seems to attract a fair number of locals, which is usually a good sign.