Think there is a misconception here...
Using Wireless@SG is as secure, or should I say, as insecure as using your broadband connection at home.

When you access your Internet Banking site, for example, your link to the bank servers is through the Internet via your ISP. So what make you think that there is no one is sniffing your traffic in between? So what is the difference if Wireless@SG traffic is not encrypted?
That is why secure sites like Internet Banking provides SSL, a link encryption layer to prevent information like userid/password and your banking information from being sniff. As the encryption is at the link layer, it does not matter that traffic over Wireless@SG is not encrypted. Anyone sniffing the wireless traffic will still not be able to see the encrypted SSL traffic.
As long as you are using Internet, just assume that someone can sniff the traffic in and out if it is not encrypted using SSL for example.
Having said that, whether you are connected over Wireless@SG or at home, keep your laptop secured by ensuring you have the latest Anti Virus signature and you have patched up any vulnerabilites reported by Microsoft or Apple.