This is a softphone application that allows you to connect to a variety of VoIP service providers, or to your own SIP compatible PBX. You can configure different profiles and switch between them (that is a desirable feature for those who like me connect with their computers to different international VoIP providers or, for instance, an Asterisk PBX).
It has all the basic call features you would expect in a softphone, like transfer, do not disturb, hold, conference, mute, and options to automatically accept or ignore calls.
Installation and setup process was really simple, and the program has a wizard to help with audio settings.
There are versions of SJPhone for Windows, Mac, and Linux and they can all be downloaded for free.
The interface is really simple and easy to understand, so if an administrator configures the telephone, users will be able to work with it easily. There are skins available if you want to personalize its look.
The only features missing in this phone are multiple lines and video streaming, but I would definitely recommend it.