I'm not into gambling. The casino is big and very business-like. It is separate from the mall. In order to go into the casino, bring your passport. Men will need to wear long pants, and no sandals (shorts not allowed). As a traveller in hot humid Singapore, I don't think it's worth the sacrifice to see the casino -- it is formal and very business-like, not fun like Las Vegas.
Tip: If you don't want to wear pants and would like to see the casino (but not gamble), you can see it from the top level. There are fancy restaurants that overlook the casino, and you can get a view of the casino. Go into the mall, follow signs to Guy Savoy. You will have to take a very hidden elevator up to the second or third level. This will put you above the casino, and you can get a view of the casino (design reminds me of Star Wars). You won't get to play, but at least you can see what the casino looks like.More