I have not try out the new twitter addon yet, but so far I have been enjoying my experience with fring. The ability to log into multiple IM application at the same time, and especially the ability to use call via Skype or via phone depending on your choice.
What draw me into fring in the first place was the ability to log in and chat & call your friends (via Skype Out) even without sim card in it as long as you can get internet access (via usb connection to your laptop or if your phone has wifi built in).
It has got everything that Skype mobile have and more. I can no longer go back to Skype mobile.
(which I don't really get why news media get so hype about Skype on iPhone when fring has been on iPhone for quite a while. Granted, I don't own an iPhone, so I don't really know how well fring works on iPhone)