I have used VoIP at work for over a decade, but I only recently downloaded Skype on my personal netbook.
The first call I received was from my 80-year old uncle in southern France. I knew he was on Skype because he had called his 94 year old sister in Canada on something she called 'Sky' though she had received the call on her land-line phone. He told me he didn't have ADSL but rather piggybacked on a friend's WiFi connection.
He is very mechanically minded, having been involved in motors all his life. In fact, he rebuilt a dozen WWII military vehicles as a hobby in the 70 and 80s, and just recently bought an 1949 MG (with all its mechanical quirks).
That said, he embraced neither PCs as they didn't meet a need, nor cell phone email as being non-real-time.
So why now?
Low cost long distance voice was clearly a factor offered by Skype.
Ease of use was critical and Skype clearly delivered in this domain with tens of millions of users worldwide.
Video was another factor due to the way my uncle wanted to communicate
I knew Skype was popular but this hit home very personally.