Excellent, cheap cocktails, alcoholic and non-alcoholic. Their milkshakes, esp blueberry, are wonderful. They do food too, but I've only tried one of their bar snacks — Devil's toast — which was nice. Food is allegedly Slovakian.
Happy hour gives you an extra 30% off all cocktails between 5.30 and 8.00.
Had (amongst others) The Guardian and New Statesman on the bar to read. Barmen are nice, unpretentious, know their drinks.
Most importantly, they make a good mojito. Which, in Oxford, seems to be the exception, not the rule.