I have used this in past, the line quality is OK for a free service. Basically when you place a call, it first shows you an advertisement and then your call is connected. You cannot minimise your screen or move it while the ad is being run
However the biggest limitation I found was that you could only make a 10 minute call per day and for any more, you gotta call the next day. For some strange reasons, my ID worked for some days and then suddenly stopped working one day. I tried reinstalling the software but no better result. I lost interest then.
Would be interesting to know other experiences