I played in the SKY Poker event there last May and it is definately wear what you like within reason. Most were fairly well dressed in the eveing but the vast majority of players wore T-shirts and jeans, not sure about trainers but I would say no. It"s an excellent venue but beware that Wind Street closes between 7pm and 7am on Weds, Thurs, Fri and Sat due to the sheer number of pissed up punters about. It"s a bit like Beruit around 3am!!