About time. I downloaded this, singed into my skype account and give it a shot. The sound quality was not all that great, but usable. Fring is NOT a jailbreak app so that means anyone can use it. The app is free in the app store, so I would grab this if you ever use skype.
The interesting experiment will be using Fring with backgrounder (which IS a jailbreak app). By running Fring in the background, you can keep your skype and/or other chat channels open while using other iPhone apps. Caution with backgrounder though, from the reports I have read, its still a bit buggy and requires a restart every now and again.