PoppaGator, I think the gas used in Guinness (and possibly other "Irish" stouts and maybe even "smoothflow" bitter) is a N₂ /CO₂ mix rather than just N₂. At one time Guinness suplied in a keg with its own gas supply used to be common but I believe that now most kegs use an external gas supply.

Joe, I'd say our English Guiness tastes good but I'm convinced the Dublin brew is even better, not that I've drunk it in a while. These days though I tend to drink "Adams", a real ale from Suffolk (England) in our Irish session. It all depends though - we get given 2 x 4pt jugs, one of Guinness and one of Adnams - I'll happily drink either...