Will this sim adapter work?

DealExtreme: $16.99 i-SmartPhone Operator Network SIM Card Unlock Attachment for Apple iPhone 3G

No, it will not. I'm not sure where you are, but I tried a TurboSim and T-Mobile SIM card in a 3G iphone and my 4GB previous generation iphone. What happens is, the 3G iphone scrolls "invalid SIM" in the upper left corner where the network is shown and on the previous generation iphone..it takes you automatically back to the activation screen where you can only make emergency calls.