I have used Skype for a couple of years now, but personally have seen the quality of calling drop in this time. If you are calling someone via dial-up then you have to put up with bigger latency (delay).
I have started using Link hidden: Login to view
which is also free calling to certain areas and very low cost to others.
The quality is at least on a par with Skype and recommended as a download as it's guaranteed no mal or spyware.
Give it a try...there are other VoIP providers out there as always.