Guinness is somewhat bitter but I think it's easy to chug because it is not carbonated the same way...it chugs more like skim milk than regular draft beer. I think I could do this easily.
On a bet I once downed a carbomb with a liter of Guinness and a pint glass-sized shot of jameson/carolyn's without stopping and it probably took about 15 seconds. A 7 second pint is very do-able...although not easy.
