Nothing wrong with Zero Degrees but IMO Copa (4 Wharton Street) is a better starting spot, best waitresses in city centre, comfy chairs, wide selection of beers - both cheap and chearful, decent guinness and expensive euro trash - plus did I mention the best waitresses in city centre. Not the biggest venue though but there"s Barocco a couple of doors away that is also very decent and a lot bigger and stays open a bit later. Then for later again or for a one-stop shop that"s open til 2am I"d vote for Dempseys (15 Castle Street), where the Guinness is the speciality, reasonable prices too. And finally for the early hours I"d recommend The Live Lounge (9 The Friary).... not that I know anything about Cardiff drinking establishments though