Unlocked 3GS, Any Problems?

Has anyone here who has unlocked a iPhone 3GS themselves (not bought an unlocked one abroad) had any issued with using any services?.

Ones like App Store, Email, MMS, Call, Texts and Web Browsing mainly?.

I know anyone can walk into a Apple/O2 store, jailbreak and unlock an iPhone 3GS in under 10 minutes but did not know if any services will be effected.

Thanks