Skype is now updated for iOS4 and supports multi-tasking. If this is not enough for you, then you should know Skype has no intention to charge you for 3G calls.
Skype for iOS4 allows the app to continue working while it’s closed. You will be able to receive IMs and calls in background, even when your device is locked. All that means Skype is capable of multi-tasking for real (only on iPhone 3GS and iPhone 4).
Skype also announced that they have no intention to charge for Skype-to-Skype calls over 3G network. All calls over 3G are free for everyone.
To update your Skype for iPhone, visit Apple’s AppStore.