a US iphone is TELCO LOCKED, means you can ONLY use it with a specific telco. You can however do a software/sim unlock, but the disadvantages significantly outweighs its benefit, i suggest u read the iphone thread regarding this.

On the other hand, ALL of the Iphones sold by Maxis are FULLY UNLOCKED, means u can use it with ANY telco and without the problems experienced by software/sim unlocked phones, plus you get a local warranty.

Please also note that the US$300 price that u see is with a 2 year contract, so you are bound by their service whether u like it or not or risk paying a hefty penalty if you want to opt out.

With iValue 4, and 2 years contract, you can even get the iPhone 3GS 16GB for free, thats $0 lol.