A full answer would take more time than I have at the moment, but yes, I've used Skype (it was our backbone communication tool for a huge project three years ago, with no funding and participants spread out over the US and Canada). It worked well enough if we fiddled around, especially the participants with computers older than last week, and didn't mind the dropouts and inaudible connections.
The list of useless/pointless tech companies that made and in some cases still make absurd amounts of money is too long to make Skype's erratic financial success a mark of quality. Nor is ANY user count that's largely nonpaying.
I spent ten years in and around the leading edge of telecom and learned enormous respect for what goes into making a communications platform reliable. Skype does not meet those standards and is in fact incapable of meeting them. It will work "well enough" as long as everything it depends on keeps working - great on sunny days, not so hot when the rain comes. In the end, there are few services that people depend on more than their phone service. When it works for you in a blizzard during a medical emergency, let us know. Because if it doesn't work at that time, no one will ever hear from you again.
