I'm using it with joomla 1.5 and I'm actually testing 3.5 before use it with my users.
I have used also previous 2.4 version and I was very satisfied to use it because all problem was releated to Openinviter and not to Parainvite.
Now with this new 3.5 that use native OAuth to retrive contact from service provider this extension is a very powerfull extension. In my test I have found some bug but I have contacted support and I have received a great support.
This extension works very good and have a great support to solve development problem. I recomended this extension to all user that searh a powerfull application for their site.
Thanks a lot.