The new Skype offers a redesigned user interface for messages and contacts and has better performance and is also reported to be more stable.
Skype for iPhone, iPod touch and iPad is free to download and works over 3G* or Wi-Fi.
What's New in Version 4.0
This version works on iPhone 3GS, iPhone 4, iPhone 4S, iPad and iPod touch. Skype requires iPhone OS version 4.3 or above.
-New feature: ability to move own video preview
-App auto restarts if unexpectedly shut down
-Updated design for contacts and messages
-New sign in screen
-Other minor UI improvements
[Read the original blog post]