Shit Guinness is basically when you order Guinness somewhere quite posh that outsells anything on tap with wine, champagne and cocktails hands down. Basically, the lines never get cleaned and you're drinking wrought iron. My girlfriend used to work in a restaurant in Hoxton (Bacchus http://www.toptable.co.uk/details.cfm/qs/rid%7C3523/spos%7C1/) that was pretty lush - a pub refurbish, no less(how lordship lane). But, as they were named after the god of wine, they didn't really shift much of the Grolsch, Staropramen, Hoegaarden or Guinness they had on tap. One of my favourite memories was a late-in-the-month Sunday opening geared towards emptying the barrels so they didn't get charged by the suppliers for returning three quarter full barrels (it was ?1.70 a pint as far as I remember - cheaper than the Saint Martins College bar no less!). I got a Guinness, took it to my table and had a sip. Nuno, the head chef snatched it away from me; "What's your favourite lager?", "Umm I usually drink Carlsberg", "Have a Grolsch, we have shit Guinness", Don't let it put you off the restaurant though, it's really very good. I hear the tasting menu is great.