I use it all the time to keep in tough with my friends in Texas. You can instant message, voice chat, and video chat all for free as long as you are doing it to another Skype client. If you want to send messages to a cell phone or call someone's phone via Skype, then their are charges.
Also, I believe there is a "premium" version that lets you have more people in a conference call and more people on a video conference call - but here is a charge for it.
Personally, I have had at least 4 ppl in a regular conference call on Skype with no troubles (using just the regular free Skype)
The only fees involved is if you want to make calls to phones, different countries priced differently. Otherwise, video calling, instant messaging (which is what most people only use it for anyway) is totally free.
Well I have never used it, my kids have, there is no fee and is user friendly
welcome and also you need to fill out a profile thingy for it