Over the years, I have to think my worst call quality experience on a consistent basis seems to have been when I am on my VOIP service and the other caller is on a mobile phone. It's not that this is always the case, but typically I am not surprised if there are issues if there is a mobile phone involved. Of course, mobile phone issues are not that unusual and my experience may have nothing at all to do with VOIP.
Is this just me or coincidence or has anybody else noticed this?