I've been to the Irish Embassy a half dozen times and I've yet to eat any food there. I go because it's a beautiful building to be inside and the brew is bountiful and cold.
Nice high ceilings and comfortable booths and tables make up the main sitting area of the Irish Embassy. There isn't a lot of separation in here so you'll be able to see everyone else who's visiting meaning it's not really the place to go if you'd like a private dinner conversation.
I've gone during the afternoon and late evening and it's always seemed like it's full of people who just got off work - the kind of work that requires you to wear a tie. Because of that it does sometimes have a slight frat boy reunion feel to it but not in an immature way.
The selection of beer is outstanding but I always stick to the native Irish ales - I feel like I'm cheating on the shamrock if I have anything not from the emerald isle while here.