Ken Camp asks Has Skype Lost Relevance?. He's observed that fewer people are using Skype today than a few months ago. True. There are now so many options for quality cheap calls that Skype isn't as exciting as it was when it first hit the market a few years ago.
It's been off my computer for several months now. Around the ETel timeframe (March or so), something in one of the releases began to interact badly with something else installed on my PC. At boot time, CPU usage would peg at 100% for 10 minutes or more, and the culprit was Skype. After spending a few hours cleaning up the PC, returning to previous versions of Skype, and not being able to determine the issue, it was time to say goodbye.
I had similar quality issues with Gizmo. Today the only VoIP client I use on a regular basis is GoogleTalk. For all other cheap calls… it's Jajah all the way. With no PC in the way, there are no worries about DLL interactions and all of that other garbage.
For me personally, it's disappointing. PC telephony has huge potential. However, if the companies bringing those products to market can't get quality under control, it will never happen for the mainstream.
Your mileage may vary. Skype and Gizmo may function perfectly on your computer, in which case I am envious.