The food is always serviceable, the service is generally good, and one of my favorite drinks can be found here.
Although it's not an Irish concoction, Brocach serves something called the Stoli Doli. Basically it's a martini made from vodka which has pineapple soaking in it all day. I was a patron of Capital Grill in Washington, DC - home of the original Stoli Doli. I like to hit Brocach occasionally when I am feeling nostalgic for my time there.
Brocach can be a little cramped, but usually it's a good time. I've certainly enjoyed myself at the various private events I've attended upstairs.